Iron and Aluminium

Salaam (May God Bless You). The iron and aluminium are two of the most important metals used today. Iron is produced in factories inside a blast furnace. The furnace has various pipes leading to it which are called tuyeres, these emit hot air in to raise the temperature. The hot air goes out through the pipes on the top of the furnace leading out. The upper hole of the furnace is where the products; coke, iron ore and limestone are added. The gases heat up the top of the furnace to 900°C and the lower part is heated to 2400°C. The carbon content in the coke reacts with the hot air in the furnace to produce carbon dioxide and carbon monoxide. The limestone is useful for helping protect

the lining of the furnace making its lifespan longer. The carbon monoxide acts as

the main reducing agent which produces pure iron called pig iron by reacting with the iron oxide ore. The pig iron is drawn off of the pipes while the slag built on top of the pig iron by the reaction between the limestone and carbon dioxide is drawn off from another end to be used as construction material. The carbon monoxide is also produced by this reaction.

Production of aluminium

Aluminium is one of the most reactive metals there is which is why it needs to be electrolyzed to be extracted from its bauxite ore. The aluminium production is done by electrolysis in Hall Heroult process. In this process pure aluminium is formed. The process is a rather difficult one as, aluminium being most reactive towards oxygen rapidly forms oxide layers on it till at least 3 nm deep. These layers are the reason aluminium can be seen as rather inert at first sight. The aluminium is useful for making alloys which are used to make aircraft vehicles. Aluminium is very soft and has low density.

Rust

Metals react with water and air to form oxides which weaken the metal and reduce its value. The corrosion of metals are called rust. It can be prevented by covering the metal with paints, plastic or even metals which are above the metallic material used in the reactivity series. The galvanization is the process in which iron is covered with zinc to act as protection. If the layer is damaged and water or air pass through, the zinc acts as the anode and the iron as the cathode which keeps the iron protected even after damage. Tinning is the same process, only difference is that iron is protected by tin which is lower than iron in reactivity series. This makes the iron the anode and tin the cathode once damaged making the rusting process faster.

 

Periodic Table

Salaam (May God Bless You). Did you knew that many of the elements in the periodic table have the atomic symbols abbreviated to their names but some have atomic symbols which are totally different. This is because these elements were given the atomic symbols according to their Latin names. Elements are generally supposed to have their atomic symbol to be abbreviated to their first alphabet in upper case letters but many have two alphabets such as Cu, C, Ca, these all have the alphabet C but represent different elements. The second alphabet is there to distinguish the elements from each other to avoid any confusion. The periods in the periodic table represent the number of shells there are in the element present in the period. The groups in the Periodic table represent the number of valence electron found on the outermost shell of the elements present.

The Group I Elements

The elements found on the group 1 and 2 of the periodic table are all metals but these are different to the commonly found transition metals as these are soluble in water and by dissolving in water these produce alkalis. These metals are also very weak and tend to break when we try to change their shape. These elements are mostly metals and are good thermal and electrical conductors. The elements are soluble in water and their reactivity increases down the row.

Group VII Elements

Group 7 elements are non metals which combine to form covalent and ionic compounds. The first few elements in group 7 are very reactive and the reactivity falls along the rows. The elements are used as oxidizing agents and can also be used for displacements reactions of any of the group 7 elements. These elements are soluble in water as well.

Group VIII Elements

The elements in group VIII are gases in room temperature and are called the noble gases. They were thought to have been inert. But in recent years many compounds have been made out of these elements. Helium is a gas whose compound has yet to be found. It is quite a beneficial gas and is preferred over hydrogen because it is inflammable. Argon is used mainly for experiments to provide and inert atmosphere.

Transition elements

Transition elements are also known as transition metals and unlike the ones in Group I, these metals are strong and malleable. These can be beaten into thin sheets. These also act as catalysts and form compounds with different oxidation states. These metals have a high melting and boiling point. These are also great conductors of heat and electricity both.

Metals

Salaam (May God Bless You). Metals are materials which are found on the Earth’s surface which is a very valuable material. Metals are sorted in to the transition elements of the periodic table and the Group I and Group II metals. The Group I and II metals are soft and are easily broken but the transition elements are very hard and ductile. They can be beaten into thin sheets. The atomic structure of the metals is as such that the metals have cations in its structure and are surrounded by free electrons. These free electrons are the cause of the thermal and electrical property of the metals. All metals are good thermal and electrical conductors. Metal cations have similar shape and size which is why they are easy to pull over each other making them ductile. This only involves the transition elements.

Extraction of metals

Metals have existed as precious materials even a thousand yeas ago in the form gold and silver. These metals are least reactive and are found at the bottom of the reactivity series. These are found in ores which can simply be heated to extract it. The metals above gold and silver in the reactivity series include copper, hydrogen lead, and mercury which can be extracted by more intense heat in air. Tin, iron and zinc are extracted by heating them and these form oxides which are then reduced using reducing agents. The last group is very reactive and thus are extracted by a means of an electric charge which is why they remained isolated until electricity was first discovered. The metals were extracted when electrons were passed through them and the cations receive the electrons, the cathode is reduced while the corresponding anions lose electrons and are oxidised at the anode.

Alloys

Alloys are mixtures of metals and/or non-metals. These are rather valuable material more than the pure metal as these have completely different properties from the initial reactants. The reason for such a difference in physical properties is that the all elements have atoms which are of different sizes which is why when two metals or non metals combine the particles are forced into shape, but they cannot be gain the same properties as before such as an alloy of copper and zinc cannot be malleable and ductile. This is because the zinc atom is large in size than copper atom.

 Reactivity Series

The reactivity series is a group of metals arranged according to their reactivity towards various materials with potassium being the most reactive and gold being the least reactive. This series also have hydrogen and carbon in it. The Group I and II are most reactive and then aluminium and then the transition elements.

Displacement Reactions

Displacement reactions are reactions between metals, one more reactive than the other. The most reactive metal will displace the electrons from the least reactive one not the other way around.

Thermal stability of metals

Metals may decompose in heat. Group I metals are most stable in high heat except for lithium, while Group II metals decompose in high heat to produce corresponding metal oxides.. The transition metals decompose readily in fairly low heat to form corresponding oxides.

 

 

 

 

 

 

 

Ammonia and Sulphur

Salaam (May God Bless You). Ammonia and sulphur are two one of the most important materials found on the earth and are produced and used worldwide. Ammonia is important due to the amount of nitrogen it contains which is precious for crops that provide food to the growing human population. Sulphur is a material used for various processes such as it is used as the electrolyte in a car battery.

Ammonia

Ammonia is a chemical produced by combining together nitrogen and hydrogen. This reaction is reversible which is we must consider the position of the dynamic equilibrium and the factors which affect the position. The forward reaction is exothermic so the temperature should be low and the pressure must be high to produce highest yield. This is a problem since the machines used to raise pressure are expensive and the low temperature slows down the rate of reaction. The rate of reaction is increased by adding an iron catalysts. The catalysts lower the need of activation energy and thus fasten the process. To further maximise its output, the Haber process is used. In this process the reactants flow to a reactor where they are combined together and then flow to a condenser where the ammonia formed is condensed out while the unreacted nitrogen and hydrogen flow back into the reactor which results in a higher yield.

Sulphur

Sulphur was founded by the famous Muslim Chemist and Alchemist Jabir Ibne Hayyan (also known as Geber) in the eight century. Sulphur is used to make sulphuric acid which is an important product. It is made by the Contact process. In this process the sulphur is first mixed with air to react with oxygen to form sulphur dioxide. The sulphur dioxide is then mixed with more oxygen to form sulphur trioxide. This reaction is reversible and exothermic which is why there is a need to raise the pressure (just a little in this case) and to lower the temperature. A reactor is used which has almost 4 bases coated with the catalyst vanadium oxide. The sulphur dioxide gas is pumped through the reactor which cools down by the first 2 bases and then is oxidised by the 3rd and 4rth base. The sulphur trioxide is then mixed with sulphuric acid to form an oleum which is then mixed with a few amounts of water to form a more concentrated sulphuric acid solution. To form a dilute solution a few amounts of oleum is mixed with a large amount of water along with stirring. We use small quantities of either materials because the reaction between sulphuric acid and water is so exothermic that the water and sulphur dioxide bubbles up and spread water out of the containers making the process dangerous.

 

Alcohols and Carboxylic Acid

Alcohols

Salam (May God Bless You). Alcohols are mostly known as beverages across the globe but in science they make a part of the homologous series. The alcohols have the functional group of -OH, this is called the hydroxyle group. The general formula of an alcohol is CnH2n+1OH. The number of carbon atoms depends upon the prefix used such meth which has 1 carbon atom in it. The suffix used will be “anol”. The alcohols also make up isomers such as propan1-ol and propan2-ol are isomers of each other because they have same molecular formula but they do not share the similarity in their physical properties.

The alcohols also burn readily in air and does not burn completely in the absence of air so produces carbon dioxide, water and carbon monoxide gas. Different alcohols can be mixed such as ethanol and methanol to form spirit bottles which provide a different source of providing flame.

Alcohols react with oxygen to form carboxylic acids. If placed in a good amount of air, the alcohol used will be oxidised to a carboxylic acid such ethanol to ethanoic acid. An oxidising agent can also be used for such process. The alcohols react with carboxylic acids to form esters.

To produce alcohols fermentation process is used which involves use of microorganisms among which is yeast. The yeast produces ethanol when allowed to grow in anerobic conditions and also produces carbon dioxide. The ethanol is a waste product which inhibits the growth of yeast once it increases in concentration and soon the yeast stops growing. The carbon dioxide helps in bread making process as it helps the dough rises in forms of bubbles. To obtain pure ethanol the ethanol is then distillated where the product should be about 96% ethanol.

Alcohol can also be produced by hydration of alkene. We could use an acidic catalyst to start the process; C2H4 (g) + H2O(g) → C2H5OH(l) ΔH = – 47kJ/mol.

Carboxylic Acids

 Carboxylic acids are a part of the homologous series with a functional group of -CO2OH and the general formula of CnH2n+1CO2H. The carboxylic acids use the same prefixes as the rest of the homologous series. The carboxylic acids use the suffix ‘anoic’ and along with the word ‘acid’. Carboxylic acids are generally weak acids becuase these have chains of carbon in them, when the chains go long and long they become more insoluble in water. Even the soluble acids are weak acids because the range of dissociation of the acids into ions is so small and the reactions a reversible. Carboxylic acids react with alcohol to form esters. Esters are formed when these two homologous series combine and the new compound is named after the two. The name of the alcohol is used first and the name of the carboxylic acid is used after, for example ‘ethyl ethanoate’.

Polymerization

Polymers are molecules formed when monomers join together. Polymers with two different monomers are called copolymers. The polymers have two ways of formation. One is the condensation method. In this method when monomers join together there is molecule which is released from the reaction which is commonly but not always water. The other method is the addition method, in which the alkenes break their carbon-carbon double bond to form longer chains of carbon. The products are named poly(name of the alkene). There are two types of polymers commonly used across the globe. The polyamide which is more commonly known as nylon. The nylon has long chains of carbon which make it hard and so it is combined with cotton to produce a better clothe. The second is the polyester which is also a famous fabric material used.

The Nuclear Atom

Salaam (May God Bless You). The nuclear atoms, the radioactive isotopes, have a radioactive nuclide which slowly loses mass to form gamma radiation. Many other types of radiation are emitted by various materials. In case of an alpha particle emitter, the isotope mass loses its protons and neutrons to form a helium nucleus. The orginal element would lose 4 nucleon number and 2 proton numbers.

Other elements emit beta particles but they do not form any ions because the neutrons divide into a proton and electron. Which is why when a beta particle is emitted the proton number of the element is increased.

The Discovery of Subatomic Particles

Salaam (May God Bless You). Elements are made of atoms which are made of three more subatomic particles which are known as proton, neutron and electron. The word atom is from a Greek word ‘atoms’ which means indivisible. It was proposed by the Greek philosopher, Democritus. He proposed that objects were made by atoms which could not be physically separated. His theory was based on reason and philosophy rather than on scientific experiments.

The Discovery of the Subatomic Particles

Then came John Dalton, an english chemist who in 1808 made several experiments along with other scientists, to give a description of the atoms. He suggested that atoms were small invisible and indivisible atoms which made up to be elements, atoms are neither created nor destroyed, atoms of same elements are identical and atoms of different elements are different in mass and size and that atoms combine to form compounds in small whole numbers. This was not entirely correct. He gave a supposed structure of the atom to be like a ball.

Then came J.J Thompson. He was experimenting with the cathode rays in 1897, he used a discharge tube which had a cathode and an anode, with two opposite charged electric plates. The discharge tube had inert gas in it which was at low pressure. The discharge tube had a high voltage of about 1500 V. He observed that the cathode rays travelled directly towards the anode and through a small hole travelled further on. It got repelled away by the negatively charged plate and attracted towards the positively charged plate. The cathode rays usually end up travelling straight without the plates. He had discovered the electrons. He then test with other gases at low pressures as well and gave following conclusions after a few more experiments; The cathode rays must be negatively charged as it got repelled by the negatively charged plate but attracted towards the positively charged plate.The cathode rays must carry a charge as they got deflected by both the magnetic and electric field. The particles present in the cathode rays must be present in all atoms. Thompson then provided another model of the atom, saying that atoms had electrons in them but since they are neutral the rest of the mass must be positive. He also identified the mass of the electrons to be the same as always.

The scientist from New Zealand, Ernest Rutherford along with his students Geiger and Marsden discovered the proton in 1910. He had set up a fluorescent sheet around a thin gold sheet and an alpha particle emitter. He bombarded the gold sheet with alpha particles and observed parts of the fluorescent sheet glow. The glowing points indicated the path taken by the alpha particles. He noticed that a lot of the alpha particles went straight through the gold sheet to reach the fluorescent sheet directly behind the gold sheet but some were at an angle away from the straight path and some were completely repelled backwards. He deduced that the alpha particles had passed through empty space which made up the nucleus of the atom and that there must be a subatomic particle with a positive charge which repelled the alpha particles. Those which were deflected backwards must have come in direct contact with the proton. He then proposed a new model for the atomic structure.

In 1932, Chadwick discovered the neutron and made the understanding of the atomic structure much more clearer. He bombarded alpha particles on to materials like beryllium and saw that it emitted rays like the gamma rays which were extremely penetrating but were not deflected in the magnetic and the electric field making this clear that these rays were neutral. He had discovered neutron and made many conclusions with this.

Then in 1913, Henry Moseley conducted experiments. He bombarded metals with cathode rays which produced X-rays. He observed that as the mass of the metals increased the wavelength of the X-rays increased as well and the square root of the frequency of the waves was half the atomic mass of the metals. This was the proton number of the elements.

 

Radioactivity

Salaam (May God Bless You). Radioactivity is the conversion of small amount of masses into energy. The radioactivity was first discovered by a French scientist, Henri Becquerel in 1896. He was experimenting with a mineral which glows in the dark. He wrapped a black paper around the mineral rock and placed it on plate in a drawer. After 24 hours, he checked the mineral and found that there was a mist on the plate which is normally seen when exposed to light. This was unusual as the mineral was wrapped in black paper. He had discovered radioactivity.

Three Types of Radiations

Since the discovery of radioactivity much work has been done by various scientists, to discover the properties of radiation. The radiations were named after the first

three Greek letters, alpha (α), beta(β) and gamma (γ). These three radiations are ionising radiations, because they impact on molecules, this impact causes the electron of the molecules being pushed out. This ionizes the molecules. This is why the radiations are dangerous to humans, they may enter the human body, ionising the cells and causing mutation which may cause a tumor or trigger cancer.

Alpha particles are positive particles of helium nucleus. These particles are large and have a great amount of kinetic energy.  This particle has two protons and two neutrons. Since it has a greater mass it does not travel far as it collides with air molecules, ionizes them and are soon absorbed. The alpha radiation is harmless to humans as it is not very penetrating but if enters the body may cause adverse affects. The alpha particles can be stopped by a sheet of paper.

The Beta Particles are negatively charged particles or more accurately electrons. The electrons have a small mass which is why the electrons have less kinetic energy. The electrons can go further than alpha radiation and can stopped by a  few millimeters of aluminium. These are very dangerous to humans as it can penetrate the skin.

Gamma radiation are waves which are part of an electromagnetic spectrum. These waves have a high frequency and very low wavelength. These waves are neither positive nor negative. Several centimeters of dense metal is required. It is very penetrating to the human body which is why it is most dangerous.

Deflection in electrical and magnetic fields

The radioactive waves are either positive, neutral or negatively charged, which is why these radiations can be passed through magnetic fields and electric fields. In an electric field, the alpha radiation is deflected towards the negative field because it is attracted towards it but is deflected by the positive field. The beta particles are deflected by the negative field and attracted towards the positive field, since the beta particles are very small in mass compared to alpha particles they are pushed in greater amount than alpha particles. Gamma radiation is not deflected but passes straight through both the magnetic field and the electric field.

Detecting Radiation

Radiation at work places such as a hospital is detected by the radiologists which wear a special badge with photographic film in it. The radiation reacts with the photographic film which is sealed from light. These photographic films help detect the amount of radiation the wearer is exposed to and is replaced regularly.

For scientific purposes, cloud chambers are used to detect the way the radiation particles move about. A cloud chamber has moist air which condenses on to the ionised air.

Geiger-Muller Tube is common device used for detecting radiation. The tube is a metal casing containing a gas at low pressure with a thin mica window in its end. The tube contains a wire with positive voltage. When the radiation enters the casing, the radiation ionizes the air which then touches the wire passing on a current. An electronic pulse counter is connected with the tube to count the level of radiation.

Half-Life

Radioactive isotopes are unstable elements which tend to decay over time. The amount of time it takes for the isotopes to decay almost half of its mass is called its half-life. The formula for half-life is t1/2. If radioactive decay occurs, the isotope then emits radiation throughout. The fall of its activity can be obtained by measuring its activity at different times. The count rate falls as the element decays and so the amount of time it takes for the count rate to fall to a value half to the initial value is its half-life.

Background Radiation

When measuring radiation of an element, we must first measure the background radiation as the ground also emits radiation which adds up to the count rate measured. The radiation is most commonly the result of the gas radon being released from beneath the Earth. To measure the count rate to an accuracy, first measure the count rate of the background radiation and subtract it from the count rate of the intended object.

Carbon-14 Dating

Carbon is an element found in almost all living things and non living things. It also has many isotopes such as carbon-12 and carbon-14. These two isotopes are constant in the environment and are constantly cycled through the carbon cycle. The carbon 14 is a radioactive isotope which tends to decay over a period of 5730 years, and so is useful for dating of dead materials or old artifacts. The carbon locks in to an organism once the organism dies, storing the carbon. Scientists burn a sample of the carbon taken from the dead organism, so that the carbon combines with oxygen to form carbon dioxide, the carbon-12 dioxide mixture and carbon-14 dioxide mixture is measured and compared to find out the date the organism died.

For example a sample od dead organism is burned to find that the concentration of carbon-14 dioxide is 3.125% its initial value, we can find out how old the organism or object is  by counting its half-life: 3.125% is the same as 1/32, we must count the half life to 1/32, 1→1/2→1/4→1/8→1/16→1/32, it has lived 5 times the half-lives of carbon-14, then we multiply the number with the half life of carbon 14; 5 x 5730 = 28 650 years old.

Organic Chemistry

Salaam (May God Bless You). Organic chemistry is the study of organic compounds found and produced around the globe. We divide the study of such materials into special groups called homologous series. The series and the study of such materials revolves around the hydrocarbons, consisting of the two elemants hydrogen and carbon. Two homologous series will be contained with in the context of this article; the Alkanes and the Alkenes. Each homologous series have their own functional group but they all use the same prefix to define the number of carbon atoms involved in each chemical, but the suffix is always different, the suffix will pronounce according to the homologous series the chemical finds itself in.

Alkanes

The Alkanes are saturated chemicals, this means that they neither have carbon-carbon double bond nor carbon-carbon triple bond. The alkanes have rather tetrahedral shaped structure but it is better to display it in linear shape when drawing for a better understanding. The general formula for an alkane is C(n)H(2n+2), n represents the number of carbon atoms. The functional group of the alkanes are C-C. The alkanes use the suffix ‘ane’.

Some alkanes may be in similar to each other in molecular formula but have different physical and chemical properties, such chemicals are called isomers of alkanes.

The physical properties of Alkanes is as such, the alkanes have weak forces of attractiong between them which is why they are volatile but as the amount of hydrocarbons increases the forces of attraction increases as well. The alkanes are gases at room temperature and are liquids in reletively lower temperatures. Other factors also count such as the color, the odour, the weight and the solubility.

According to the chemical properties of the alkanes, these are inert chemicals but do have some significant properties. Such as combustion, the alkanes burn readily in presence of air to release water vapour and carbon dioxide but in the absence of air the alkanes do not burn completely and produce the gases carbon monoxide and water vapour and also carbon itself. The carbon monoxide gas is a poisonous gas, this reaction is also less useful as not a lot of energy is released.

Chlorination is another way of describing the chemical properties of alkanes. The alkanes are inert but when they come into contact with sun light they rapidly start a reaction and it is so fast that it can not be controlled and results in a lot of products being formed such as CH3CL, CH2CL2, CHCL3 and CCL4.

Alkenes

Alkenes are unsaturated hydrocarbons which have a carbon-carbon double bond. The functional group of the alkenes is C=C. The alkenes use a suffix ‘ene’. They have a generla formula C(n)H(2n). The isomerism and the physical properties of the alkenes is similar to that of alkanes but not the chemical properties.

The alkenes are very reactive chemicals, they burn readily in air just as the alkanes and have the same affect as alkanes when burned without air. The alkenes also react with bromine to form 1,2 – dibromoethane. The bromine reacts safely across the carbon-carbon double bond. CH2=CH2 + Br2 → CH2Br – CH2Br. Other alkenes also react with bromine, chlorine and iodine the same way.

Alkenes react with hydrogen to form an alkane. The hydrogen molecules reacts across the carbon-carbon double bond to add to the hydrogen in alkenes making, it an alkane: CH2=CH2 + H2 → CH3-CH3. This reaction requires the involvement of a nickle catalyst and the temperature of the mixture needs to be over 150°C. This process is called hydrogenation. This is a useful technique to break longer bonds of carbon into smaller ones to form various products. Alkenes also build up to large molecules called polymers. This process is called polymerisation.

Cracking alkanes to become alkenes

Clearly alkenes are better than alkanes. The sources of such chemicals is found in the natural gas, and crude oil but these mostly contain the alkanes. To make alkenes out of the alkanes we crack the long chains of carbon into short chains. There are two ways, one is steam cracking, where a mixture of hydrocarbons and steam are in a cracking furnace around 750 – 800°C. The other methode is the use of a catalyst in a mixture of hydrocarbons through a reactor at around 500°C. Later the products are separated by fractional distallation.

Acids, Bases and Salts

Acids

Acids are known for being corrosive and sour but in truth acids are defined due to their tendency for relieving hydrogen ions in an aqueous solution. There are two types of acids, organic acids and inorganic/ mineral acids. Organic acids are found in plants and animals and are helpful rather than being harmful in most cases. Organ acids are more commonly found in the fruits we eat. The inorganic acids or mineral acids are found in Labs throughout the world, one example is the sulfuric acid.

These types of acids are more commonly known due to the properties, which are, turning blue litmus paper red, having a sour taste and being corrosive. These acids are used either in dilute form or concentrated form but in either case safety is necessary which can be ensured by wearing gloves and eye protection. When carrying bottles of corrosive acid, make sure to place it on a tray so that it does not damage the surface of the table or floor or whichever surface it is placed in.

All acids have almost the same structure and the same chemistry. The acids are determined to be either strong or weak by observing the amount of hydrogen ions they release in aqueous solution, such as a hydrochloric acid solution is mixed in water and is completely ionised, indicating it is a strong acid; HCL + H2O → H+ + Cl-, in case of acids like ethanoic acid, the acid is not completely ionised and so, is a weak acid but since it is a reversible reaction, the sign “↔” shows that the reaction is not complete and also indicates that the reaction is continuously using and discharging the hydrogen ions: CH3COOH + H2O ↔ CH3COO- + H+.

The same situation is used to determine the basicity of an acid. Such as HCL only releases 1 hydrogen ion per reaction thus is a monobasic acid, Sulfuric Acid releases 2 hydrogen ions per reaction and so is a dibasic acid, a phosphoric acid is a tribasic acid which releases 3 hydrogen ions.

Acids react with metals to release salt and hydrogen gas, they react with metal carbonate and hydrogen carbonates to release carbon dioxide, the acids also react with bases to form salt and water.

Bases

Bases are all those chemicals which release hydroxide ions and oxide ions. The bases also react with acid to form salts and water. These type of reactions are more commonly known as neutralization reactions because the resulting products water and salts are neutral, neither acid nor basic, with a pH of 7. Bases are mostly metal oxides and metal hydroxides which do not dissolve in water but there are bases in Group I and some in Group II of the periodic table, including ammonia, which dissolve in water. These bases are known as Alkalis.

Acids, Bases and Amphoteric oxides 

Acid oxides are those oxides which dissolve in water to form acids. Base oxides are those metal hydroxides or oxides which react with acids to form salt and water, but in cases of Group I and Group II Bases we can say that these metal hydroxides and oxides react with water to form an alkaline solution. The Amphoteric oxides are those base oxides which react with acids to form salt and water but also act as an acid and react with other bases to form salt and water as well.

Preparing Salts

Salts are neutral compounds (in most cases) formed when acids react with bases. Salts are formed when the hydrogen ions in an acid is completely replaced with metal. In some acid-metal reactions, metals do not replace the hydrogen ions completely because the compound is likely to have more hydrogen ions than 1, therefore the salt formed will be called an acid salt.

Salts can be prepared, by reacting acids with metals, which are above hydrogen in the reactivity series, or by reacting acids with metal carbonates or even reacting acids with bases. In any case the most affective way of carrying out the reactions is by the use of titration method. This method involves the apparatus; a conical flask and a burette. The burette is filled with an acid while the conical flask is placed underneath it with a base, there is an indicator mixed in it. The acid is poured to the point where the color of the mixture changes, the mixture is stirred along the reaction. When this happens the initial chemicals are again used according to the new measurements and then the mixture is heated and then set to cool and crystallize. This is done because the last mixture has an indicator in it which makes it useless because the salt is needed in pure form.

Universal Indicators and the pH scale

To detect whether a solution is acidic or basic we use various indicators to show us this. There are many indicators used across the globe, most common one is the litmus paper which may be in red or blue and change into latter when placed in an acidic or alkaline solution. But such indicators are not useful if we were to detect the exact amount of acidity or basicity of the solution. For such reasons we use the universal indicator which has many indicators joined up to form one whole scale which can detect various ranges of acidity and basicity. The pH scale is used to number the amount of acidity and basicity of a solution. The pH scale was introduced by the Danish chemist SP S∅rensen in 1909. The pH is the abbreviation for “potential for hydrogen”. The pH has a range of 0 to 14 and being a logarithmic scale, each range is 10 times greater than the last, meaning an acid with a pH of 3 is 10 times more acidic than the acid having a pH of 4. The pH 7 is supposedly neutral solution.

Practical Electricity

Salam (May God Bless You). Todays article is Practical Electricity. It will feature information about electrical components which we observe in our daily lives but sometimes just ignore it because we lack the knowledge of the importance of such components.

Direct and Alternate currents

In smaller circuits we use batteries and cells to provide with sufficient amount of energy, these sources of energy provide a direct current, d.c, which means it will not change its direction. If we observe the direct current in a p.d against time graph we can see that the d.c can be negative or positive but will not change its p.d. To represent the symbolic form of the d.c then we just draw a cell or battery to represent a direct current.

An alternate current, a.c, is a current which can change its direction. It is mainly provided by a mains supply. If a.c is observed in a p.d against time, then we can see that an a.c current changes its p.d over time, meaning it might be negative or positive in the next few seconds. To represent the alternate current we use the shown symbol.

Electrical Apliances using electric heating and electric lighting

Electricity is used in homes and offices for apliances which use the electricity to convert the electrical energy into other useful forms of energy. This is very useful as electricity is a clean energy and does not produce any waste. The electrical energy is converted mostly into heat energy, espacially in those appliances which use it for such purpose.

Such appliances have a special rod or a piece of wire which is an alloy of chromium and nickle, called a nichrome. Such rods have a very high melting point. The rod has a lot of resistance and therefore the electrical energy is conveted into heat energy. In appliances like a heater it is used as a rod but in appliances like a kettle it is used as wire insulated from the water in the kettle which helps heat it up.

An incandescent or filament bulb uses the electrical energy to convert it into light and heat energy. The bulb has a filament in it made of a metal called tungsten which also has a high resistance, about 3422°C. When a current passes through it, then the filament converts almost 10% of the energy into light energy while the rest is converted into heat energy which is why after a short time the bulb heats up. The bulb has an inert gas inside it which may be argon or nitrogen, we use these gases because the tungsten can react with oxygen and may cause an explosion.

An alternative to the incandescent bulb is the fluorescent bulb. The bulb has two electrodes in it and mercury vapour, the inside surface is coated with fluorescent powder. When the electrodes are powered, the mercury atoms become agitated and they release ultravoilet radiation. The ultravoilate radiaiton is absorbed by the fluorescent powder which causes it to glow.

Power

Power is the rate at which energy is transformed into another form of energy. This is also known as work. Therefore for electrical devices we use the formula: P = IV, P is for power, I is for current and V is for voltage.

For energy we use the equation: E=IVt, E is for energy, I is for

Three pin Plug

The mains electricity is used up by connecting a plug with a socket. The most common type of plug used is the three pin one. It has three pins, two lower pins which are short and the top pin which is longer than the lower two becuase it is used to open the grates in the socket holes which connects to the lower two pins. This is a safety measure to prevent anything to be pushed into the socket.

First of all the plug has a plastic casing which serves as an insulation from the electricity which can be hazardous. The inside of the plug has cable clamp in it which grips the cable tightly enough to prevent it from falling out when pulled or tripped over. The plug has a fuse in it connected with a live wire. The plug also has a neutral wire and an earth wire which is connected to earth. The wires are color coded; neutral wire is blue colored, live wires are brown colored, and an earth wire is either yellow colored or brown colored.

Safety Measures

The safety measures in a circuit is in several forms. The most common one is the presence of fuses in a circuit. Fuses contain small pieces of wire contained in a ceramix container, these wires can only carry a certain amount of current like 5 A, or 7A but whatever the limit, if the current exceeds the limit, the wire melts causing the circuit to be broken. This is useful as in an appliance there are many components which make up to a lot of resistance but sometimes wires get cross connected causing a new circuit being made which reduces the resistance of the circuit and therefore increases the current. This is very dangerous and can give the user a shock if he/she touches the appliance. To avoid this fuses are plugged in which break up the circuit in case of an increase in current.

An appliance also has an earth wire mainly in its plug. The earth wire is connected to the earth which causes the current to flow to the earth in case it rises above the limit. This is a good safety measure and can prevent you getting electric shocked. Another safety measure is that appliances may be covered with an insulator like plastic making it double insulated. Even if the inside circuit gains a boost of current it won’t affect the outside layer of the appliance, these kind of appliances do not need an earth wire.

DC Circuits

Salam (May God Bless You). This article is about drawing circuits in their symbolical form. Since drawing original shapes of the component is very difficult we use symbols to represent the actual electronic components. This is useful as these ssymbols are understood universally and are easier and quicker to draw.

Connecting In Series and Parallel

Electrical components such as bulbs are connected in a circuit either in series or in parallel. We can see the effect connecting components either way if we connect two bulbs as such. If connecting two bulbs in series, we can connect an ammeter on either point of the circuit to find that the current is same everywhere on the circuit. In case we connect a voltmeter in parallel to the bulbs, we can see that the p.d across each bulb is same and the total p.d of the bulbs make up the potential difference equal to the battery itself. By connecting more bulbs causes all the bulbs to lose their brightness soon and will break.

In a parallel circuit, the amount of components connected will not matter to much but if you keep on adding components like a bulb they will soon burn out. If one bulb burns out this does not affect the other bulbs like it does in a series circuit. This is because the parallel circuit makes up two circuits in principle, due to this the current gains two paths to move.

When we connect an ammeter to various parts of the parralel circuit, we can observe that the current in both parts of the circuit is same but on the other part of the circuit where the two currents meet we see that the amount of current is different, the sum of the two currents make up the total current. If a voltmeter is connected across the circuit, then the p.d across both components will be equal to the battery itself. This proves that the parallel circuits do not last as long as a series circuit but will be more efficient.

Diode

A diode is made by silicon which is a semi-conductor. What a diode does is that it controls the direction of current flow. If a diode is in a forward position, this position is called forward biased, then the diode will help move the current forward only and no other direction. If it is connected in reverse then the diode will be negative biased and no current flows through the circuit.

Light Emitting Diode (LED)

A light emitting diode acts as a simple diode but emits light which is very useful to know whether a circuit is working or not. Today many led bulbs can be bought as an alternative to a conventional bulb but they are expensive but much more efficient to the conventional bulbs.

Thermistor

A thermistor is resistor which depends upon the temperature. When the temperature increases then the resistance decreases and vice versa.

 

 

Electronic Circuits

Current

When electrons are pumped across a circuit, a charge is produced. The charge is given the unit of coloumbs. The movement of the charge per second is called current. It is measure in Amperes or amps (A) and is measure by an Ammeter. To find the amount of current passing through a circuit we use the equation:

I = Q/t

I is for current, Q is for coloumbs of charge, and t is for the amount of time in seconds for the charge to pass.

Electronic Symbols

These symbols are used to represent components or conductors that are normally involved in a circuit. The circuit is drawn in symbols with lines to represent wires becuase this way the circuit is understood by all and is not much time consuming. Here are a few electronic symbols used.

Ammeter

An ammeter is a device used to measure current passing through a circuit. There are two types of ammeter, one is analogue which has a needle and a scale on it but a digital ammeter is more commonly used due to its diverse use. The digital ammeter can be connected to a multimeter for other uses such as measuring Volts. A digital ammeter may have a range of 0 – 10A which can by modified by a shunt. A shunt has thin wire in it which can divert the current to flow through it allowing the ammeter itself to measure a small amount of current, this is how the range of an ammeter increases. For example a shunt has been set at 90%, then the range of the ammeter will be increased to 0 – 1A. Ammeters are connected in a series circuit.

Prefixes used for Amperes and Volts

The current that flows through a circuit is normally below 1 which is why special prefixes are used to calculate the Amperes of currents that flow through.

• MilliAmpere, mA is the unit which is the 1/1000th of an ampere therefore a 1000 mA is equal to 1 A.
• MicroAmpere, µA,  is 1/10000th of an ampere so 10,000 µA is equal to 1 A.

Although millilivolts and micro volts are not used much but have the same have value as the prefixes for Ampere.

• MilliVolt , mV, is 1/1000th of a Volt therefore 1000 mV is equal to 1 V.
• MicroVolt, µV, is 1/10000th of a Volt therefore 10,000 µV is equal to 1 V.

Combining Cells

Cells can be combined to make up 1 battery. Cells may be placed in same direction causing an increase in potential difference, for example two cells having p.d of 1.5 V will make up 3 V if placed in same direction.

If cells are placed in opposite direction to each other then the resultant p.d will be the difference between the p.d of both cells, for example two cells having p.d of 1.5 V will make up total p.d of 0V.

Potential Difference

When a cell is connected to a circuit it forms two terminals, one is positive while the other is negative. These terminals have a difference in energy and this is because this difference is called potential difference. This difference causes the electrons to flow from the negative terminal to the positive terminal. The p.d is measured in Volts which is why it is sometimes called the voltage. The voltage is the reason a charge flows through the circuit. The greater the p.d the greater the charge flows throught the circuit. The p.d also affects the rate at which the electrical energy changes into other forms of energy.

The greater the p.d the faster the rate at which the electrical energy is transformed. For example a circuit with a bulb in it has p.d of 240 V will be brighter and hotter than a bulb in a circuit having p.d 12V. To calculate this work done, i.e; electrical energy changed into a different form of energy, we use this equation: W = I x t x V. The voltage or p.d is measured by a voltmeter which may have a range from 0 – 10 V. The Voltmeter can be connected to a multimeter to serve various purposes. It can be connected with a multiplier to increase is range. The voltmeter is connected in parallel to a conductor to measure the p.d across it.

Resistance

A circuit may have a lot of conductors in it which is why different currents flow through them. This is because each conductor has different resistance towards the flow of the electrons. Resistance is basically the ease at which electrons can flow through a conductor. The easier it is for the elctrons to flow the less resistance there is against it. Resistance is measured by ohms, Ω.

Resistance is used to control the flow of current and is done so by resistors. There are two types of resistors fixed resistors and variable resistors. The fixed resistors have a fixed resistance but variable resistors can have a varied amount of resistance. A Light Dependant Resistor (LDR) depends upon light. If it is placed in front of a light source, its resistance drops while placing it in the dark will increase its resistance.

Resistors in Parallel and in Series circuits

Resistors can be connected in a series. This results in various different p.d to be formed between each resisitor. The Voltage can be calculated as V = V1 + V2 + V3. Resistance in such a circuit is calculated by R = R1 + R2 + R3. To find the resistance the formula used is R = V/I. V is for Volts, R is for Resistance and I is for current. Resistors can also be connected in parallel circuits. The total resistance in this instance is calculated

by 1/R = 1/R1 + 1/R2 + 1/R3. The voltage across the parallel circuit remains the same. The total current will have to be calculated by the equation: I = I1 + I2 + I3.

Ohm’s Law

The Ohm’s Law says that the current through a metallic conductor is directly propertional to the p.d across it, if other factors such as temperature is constant. We can prove this by increasing the temperature of a circuit which has a ohmic conductor in it, as the temperature increases the resistance of the ohmic conductor also increases. If a bulb filament is heated its resistance will decrease showing that all semiconductor or insulator will lose its resistance once heated.

Resistance of a Wire

Resistance of a wire is directly propertional to its length and is indirectly propertional to its cross section area. If a wire is long it has more resistance than a short resistance and if a wire is thin it has more resistance than a thick wire. Resistors more commonly have a short length of carbon in them, which in some cases have a long wire winding around the ceramic rod in a casing. This makes it cheaper.

Electromotive Force

Electromotive force of a source of electrical energy, such as a cell, is the total p.d of the cell when a circuit is open. For example a cell having a p.d of 1.5 volt on an open circuit will be its e.m.f but when the circuit is closed and if there is a conductor such as a bulb in the circuit ther p.d will decrease due to the internal resistance of the cell. Therefore e.m.f is the work done ÷ charge.

Since 1 V is equal to 1 J of energy, and not all the emf is used then the difference in the p.d of an open and closed circuit will be the wasted energy. The equation to find out EMF is E = V + Ir. Ir is for internal resistance, and E is for EMF, and V is for Volts.  When cells are connected in a series then the total resistance of the cells is R = r + r + r. If the cells are placed in parallel to each other then the total resistance of the cells is R = r/3. The lost p.d can be found by the equation, Lost p.d = I x r. Then the result can be subtracted from the EMF.

Redox Reactions

Salam (May God Bless You). There are some reactions called oxidation, in which substances gain electrons, these substances also may gain oxygen or lose hydrogen atoms which is why the reactions are known as oxidation. Other reactions are known as reduction, the substances involved in such processes gain electrons, they may also lose oxygen atoms or gain hydrogen atoms. These two reactions do not occur in isolation but together in a reaction and are thus called redox reactions.

Oxidising agents

Oxidising agents are those agents which oxidise a substance while they themselves are reduced to atoms. The mose commonly used oxidising agents are Non-metallic elemants which accept electrons to form anions, metal cations which accept electrons to form a complete atom, and those ions which contain an elemant which has a very high oxidation state which is lowered in the process.

The Oxidation state is the amount of charge an ion carries such as Na+ has the oxidation state of +1.

Reducing agents

Reducing agents are chemicals used to bring about reduction while they themselves are oxidised. The most common reducing agents are metals which donate electrons to form cation, non-metals which remove elemants with negative oxidation state during a reaction, and Ions that have a low oxidation state but during a chemical reaction they rise in their oxidation state.

Reversible reactions and dynamic equilibrium

Some reactions are written on a piece of paper with the sign “→” indicating the reaction is only in the forward direction, meaning that only products are formed. Other reactions have the symbol “↔” indicating a reversible reaction. This means that the reaction can produce such products which again react with one another to form the initial reactents. These kind of reactions are called reversible reactions.

These reactions do not occur at the same rate but there comes a time when the concentration of the products and the reactents formed are in the same equilibrium state. The products and reactents have the same concentration in the same state. This state is called “dynamic” because the reaction is continuous.

La Chatelier Braun Principle

The principle was founded by the French-Italian chemist Dr. Henry Louis Le Chatelier and the German physicist Nobel laureate Karl Ferdinand Braun. This principle is more commonly known as the Le Chatelier Braun principle. The principle states that when a chemical reaction is in the state of dynamic equilibrium, if the external factors such as temperature is not constant then the state of equilibrium will shift to the side which will try to prevent such a change.

For example, if the forward reaction in a chemical reaction is exothermic then the reverse reaction is endothermic. If the temperature is raised then the equilibrium will move to the left side causing more reactents to be formed.

In case of pressure, if the pressure of the reactents is increased the equilibrium state moves to the right meaning more products are formed than reactents. If the moles of both the reactents and the products are different then no matter which side has the most pressure then the equilibrium state falls to the side with less concentration/moles.

Rate of Chemical Reactions

Salam (May God Bless you). Today I am writing about chemical reactions and the factors which affect them. Chemical reactions are ways in which useful materials and compounds are formed and these reactions are also used to observe the rate at which the chemical reaction occurs.

Rate of Chemical reactions

There are various chemical reactions. Some are so fast which occur so fast that they occur in a blink of an eye, while others are so slow that we fail to see their existence. During a chemical reaction, the concentration of reactents decreases while the concentration of the products increases. The rate of reaction is the amount of products produced over a period of time or the loss of mass of the reactents during a certain amount of time: Loss of concentration of reactents or gain in concentration of products / time. 

Some chemical reactions produce gases which can be observed with a gas syringe. There are three types of reactions commonly used to observe the rate of reaction, one is the reaction between a simple metal with a dilute acid, one is reaction between a metal carbonate with a dilute acid, and the last one is a reaction between thiosulfate and dilute acid. The first 2 reactions produce gas. Calcium carbonate and dilute acid reactions should be avoided because calcium sulfate is produced which is a precipitate of the reaction, it makes it hard to observe any changes in the chemical reaction.

To show the rate of reactions on a graph we use a rate curve. The rate curve shows the loss of concentration of reactants over a certain period of time and may also show the amount of products formed over time. The factors to know about a rate curve is:

• The steeper the rate curve, the faster the rate of reaction.
• The rate of reaction is always greater at the start of the reaction.
• When the rate curve becomes horizontal then the reaction is complete.

Collision Theory

The collision theory was inspired from the kinetic particle theory, according to the collision theory, the particles of the two reactents react with each other by collision. The particles of the two reactents collide to start a chemical reaction. The factors to know about the collision theory is:

• The reaction will not take place until the particles collide together.
• The particles have a certain amount of energy which when collided combines and then forms enough energy to activate the reaction. If the energy is not enough then the reaction will not take place.
• The particles should have a complimenting geometry for colliding and starting a reaction.
• If the particles are heated then the particles will gain a lot of energy, enough to collide faster.
• This does not mean that all the particles colliding will start a reaction, but the reactions which start are all due to the colliding particles as some particles do not have a sufficient energy.

Catalysts

Catalysts are those chemicals which alter and most often increase the rate of reaction without being chemically changed itself. This is because a catalyst provides an alternate path towards the start of the reaction and lowers the activation energy needed for the chemical reaction. Most catalysts are transition elements while others are compounds of transition elements. Some catalysts actually even lowers the rate of reaction and are called retarders or inhibitors or even negative catalysts.  Those which increase the rate of reaction are called positive catalysts.

Factors that affect the rate of reaction

Temperature

If you have read my post kinetic particle theory and Energy from Chemical Reactions you will know that once heated, the heat energy will be converted into kinetic energy in the particles and will vibrate vigourusly. This causes the particles to collide much more quickly and will result in a quicker rate of reaction. However if the temperature falls, then the bonds between the particles will soon form much more stronger and the rate of reaction will slow down so much that it would seem to have stopped completely. This is because, the particles will collide much more slowly.

Concentration and Pressure

If the concentration is high then there will be more particles needing to collide to complete the reaction which is why the higher the concentration is then the slower the rate of reaction is. In case of pressure the higher the pressure the faster the rate of reaction will be.

Catalysts

The presence of a catalyst in a reaction will also affect the rate of reaction. If using a positive catalyst and in a good and specific quantity then the rate of reaction will be faster.

Surface Area

The surface area of an object depends upon how small the size of the object is. Such as a things as small as a tablespoon of powder has a large surface area while a cube of same mass has the smallest surface area. If you add a teaspoon of powdered sugar in your cup of tea it will dissolve much more quickly than a few cubes of sugar with the same mass. This shows that the larger the surface area the greater the rate of reaction.

Static Electricity

Salam (May God Bless you). Static means standing still. In case of electricity we mean to say that electricity does not just pass on in a matter of moments through an object, like everyone believes, electricity can also be stored or built up in an object or more specifically an insulator. The reason for this is that most conductors are metal and metals have a sea of valence electrons in its lattice. These electrons are mobile and thus can carry charge around the whole metal causing the electrical energy to pass on quickly. An insulator is deprived of this much electrons causing the electrical charge to build up in it.

Static Charge by Friction

Static charge is mostly done by friction. Friction is the resistive force against any  moving object. This force causes the formation of electricity which builds up in an insulator. If you walk on a nylon carpet and touch a door knob, you will feel a tingle on your finger, this is due to discharge of the electrons from your finger. Even in our atmosphere static electricity is produced. The warm and cold bodies of air pass through each other and due to the friction of their movement static electricity is formed, when it is formed in excess, it is then discharged in the form of lighting, this is also accompanied by an explosion we call thunder.

What happens when you rub two insulators is that, when they are rubbed off, electrons are passed from one insulator to the other insulator, leaving one object positively charged while the other negatively charged. The charge the both objects carry is equal but opposite.

Two types of charges

There are two types of charges one being negative and the other positive. We can see the effects of such charges by charging two glass rods with silk and placing them together, we can see that they repel each other. If we charge an ebonite rod and place it in front of a glass rod, they attract each other. We can say that two carry an opposite charge, while the two glass rods carried the same charge.

When a positively charged object is touched, the electrons will flow into the charged object from earth. When a negatively charged object is touched, the electrons flow from the object and into the earth. This is a simple method of discharging an object.

A positive charge has currents flowing outwards, while a negative charge has current flowing towards it. If you put two objects which have the same charge the two charges will repel each other but the charges which are opposite will attract each other.

Why Charged objects Interact?

The Ancient Greeks first noticed that when amber was rubbed on a fur, it would gain unusual properties. The amber could attract small pieces of various objects. In the 16th century, the famous physicist Dr. William Gilbert, then observed this property much more closely.

What happens is that if a positively charged object such as perspex ruler is placed on top of a few bits of paper, the bits would be attracted to the object. This is because the papers have an equal and opposite charge in them. Meaning it has both the positive and negative charge which is evenly distributed across the paper.

When the ruler is placed on top of it, the negative charge moves towards the side where the ruler is and the concentration of the negative charge is increased on one side of the paper while on the other side the positive charge is in higher concentration. This causes attraction between the two things. This whole process is called electromagnetic induction.

Van Der Graaf

A van der Graaf is large insulated metal dome which uses static electricity to charge itself. It is charged by a rubber rubbing off on a perspex bar. If you touch it while standing on an insulator, your body will be charged.

The reason your hair looks strange is because every single hair is charged the same and will repel each other. There is a smaller sphere near the van der Graaf which is connected to the earth, it will take away the electrons of the Van der Graaf.

ElectroScope

An electroscope is a piece of apparatus. It is useful to check whether an object is charged or not. It consists of a brass cap, a brass rod and a brass plate. The brass rod is insulated from the metal jar. The jar is covered in glass and is earthed. There is a metal leaf with the brass plate which is normally made of gold. If a positively charged object is placed above the brass cap, electrons will flow into the brass cap using the same principle as the electrostatic induction.

The brass plate and the metal leaf will both be positively charged which will cause them to repel. In case of a negatively charged object, same effect occurs, only that the brass cap will be positively charged while the metal leaf and the brass plate will be negatively charged. 

If you touch the brass plate or just connect it to the earth directrly during the experiment, the electrons will flow into the earth, causing the electroscope to be positively charged entirely, this will cause the metal leaf and the brass plate to repel. The same effect occurs when using a negatively charged object, only difference is that the electrons will flow in to the electroscope from the earth in this case.

 

Magnetism

Salam (May God Bless You). Magnets are popular for many uses and are most important for making various infrastructure or complex circuits. Magnets are also used in the labs for various testing. Did you knew that magnets were first discovered thousands of years ago when people noticed a certain rock named lodestone having a very unusual property. If the rock was left hanging from a rope or placed on water, it would always point to the same direction. At the time no one had the idea that the rock actually had a magnetic property in it.

The reason it did this was because it always pointed towards the magnetic North Pole. This feature was then used as a compass which aided travellers when they couldn’t take bearings from the stars and the Sun. This rock is now known as magnetite and it is a well-known permanent magnet. Other permanent magnet materials are iron, steel, cobalt and nickel, etc. Materials which are attracted to a magnet such as these are known as magnetic, while the other materials are non-magnetic which are aluminium, copper and brass.

Properties of magnets

Magnets have their properties because of the magnetic field which surrounds a magnet. If drawing a diagram , the magnetic field is shown by the field lines and the stronger the magnetic field the more concentration of field lines there will be. The field lines always come from the North pole of a magnet, and to the south pole of the magnet. The picture other than the magnet you see is a solenoid which will be discussed later in this article.

To know why there is such a magnetic field, we should consider that there are tiny magnetic molecules or tiny magnets in a simple material such as iron which are unaligned. When magnetized, the tiny magnets will become more aligned such that it will be directed towards the North pole of the magnet. This causes the formation of magnets.

Some materials, when magnetised, retain its magnetism for a long time which is why these are called permanent magnets. These materials are named “hard” for this reason. Other materials remain magnetised for a very short amount of time which is why they are called “soft”.

The other properties to discuss is the law of magnetic poles. Every one knows that if two same poles are placed in front of each other, they repel each other off while putting the opposite poles of two magnets in front of each other causes the two magnets to be attracted to each other. This is also useful for finding out whether a material is a magnet or not. If you place two objects together with the same poles facing each other, one a magnet and other a magnetic material, if these two repel each other this means the magnetic material is a magnet.

The reason behind this is that the field lines come out of the North pole while it is taken in by the South pole, causing the two to be attracted while if you place two south poles, field lines are deflected and a null point is formed in the center.

Another property of a magnet is that when a magnetic object attached itself to the permanent magnet, the object becomes a magnet itself and attracts other magnetic objects towards it. This situation is called a magnetic induction. For example if you place a horseshoe magnet over a bunch of steel paper clips, the same effect will take place.

Magnetising

There are three ways for magnetising. One method is to use a single touch method. In this method, we stroke a straight iron bar with a magnet several times. If the North pole is used, the side that is first touched by the magnet then it will become the North pole while the other side will become the South pole. 

The second way is the double touch method. We use two magnets for this. On an iron bar, stroke a magnet from the center of the iron bar to the end using the south pole, while stroke the other end from the center to the opposite direction using the North pole. This will cause the iron bar to take the opposite polarity that the pole used to stroke it.

The last method is to use a coil of wire called a solenoid. Place an iron strip in the solenoid and pass the current. The current forms a magnetic field around the wire causing the tiny magnets in the iron bar to align and form a magnet. To find the North pole of the newly formed magnet, place your right hand on the solenoid and curl your fingers as such that the fingers point towards the direction of current. The direction the thumb points is where the North pole is.

Demagnetising

If you heat a permanent magnet or hit it by a hammer several times, it will lose its magnetism. This is because the tiny magnets gain kinetic energy due to these actions and vibrate vigorously, causing them to lose their alignment. Another way is that if we again put the magnet in a solenoid and pass on an alternating current (a.c), and slowly remove the current, the magnet will lose its magnetism.

Magnetic field around a current and a coil

If you pass a current through a wire, it will produce a magnetic field around it. The direction of the field depends upon the direction of the current itself. If the current moves downwards then the magnetic field is clockwise and if it moves upwards, the magnetic field is always anticlockwise. A fact to note is that when a solenoid has a current passing through it, the solenoid will have the same magnetic field as a bar magnet. When a wire moves around in a circle through a cardboard, there will be two magnetic fields formed. The first will move anticlockwise and the other clockwise.

Energy From Chemical Reactions

Salam (May God Bless You). Chemicals are associated with energy more closely than what you might think. Chemical reaction starts off due to energy on the first place. As the reaction undergoes chemical changes, energy is taken in or given off depending upon the type of reaction whether exothermic or endothermic.

Activation energy

A small amount of energy is required to start off a chemical reaction, even if the chemical reaction results in giving off or taking in a lot of energy like an explosion. This amount of energy is called activation energy. It is denoted by Ea.

Enthalpy

Enthalpy is the amount of internal energy involved in a system of imput, processes and output. It mainly revolves around the internal energy of the reactents and the products. The change in enthalpy is denoted by ΔH. Enthalpy is always negative in case of an exothermic reaction because energy is given off as heat energy and will always be positive in case of an endothermic reaction because energy is always taken in from the surroundings as heat energy.

Combustion

Combustion is an exothermic process. Combustion is the type of chemical reaction used to release heat and light energy. The fuel for combustion is most commonly the fossil fuels. The fossil fuels are a result of the organic life being trapped under sediment and due to the decaying of the organic life, carbon and hydrocarbons were stored in the rocks. Coal is only carbon, meaning when it burns, it will combine with the oxygen in air to form carbon dioxide, CO2: C2(g) + 2O2(g) → CO2(g). Crude oil and natural gas are mainly hydrocarbons. Crude oil however has other elemants such as nitrogen, sulfur, and other metal carbonates.

Hydrogen as a fuel

Hydrogen is a flammable gas. It provides a lot of energy per gram. It is a very useful source of energy, this isnot only because it provides large amount of energy but also because it does not pollute the environment. When burned it produces water vapour: 2H2 (g)+ O2(g) → H2O(g). The oxygen is already present in the air. Hydrogen is also a very reliable source of energy because it is in vast amounts in the form H2O, water, since Earth is 71% water. Other than that when burned it again turns into water, making it reusable. Hydrogen can be obtained by either decaying of hydrocarbon or by electrolysis of water. However the disadvantage of this is that hydrogen is hard to store in gas form and requires special containers. It is still not effectively obtained making it difficult to use. The hydrogen gas is highly flammable and when mixed with the atmospheric air, it can cause a huge explosion when burned.

Hydrogen fuel cell

Hydrogen fuel cell is used for the purpose same as a electrochemical cell. Only difference is that the cell uses hydrogen as the fuel in gas form, hydrogen passes into it from one side and on the other side oxygen gas is passed in as an oxidising agent. There is also a catalyst present which helps with oxidation of hydrogen. The cell has two electrodes in it with the electrolysis. Hydrogen turns into cations at the anode and moves to the cathode, then reacts with the electrons and with oxygen to form water. This whole process results in a charge being formed that is passed along the circuit.

Composition of Crude oil

Crude oil is composed of hydrocarbons. Its components include naptha, feul oil, gas oil, and kerosene. It cannot be used in its raw state, but it can be filtered, by distillation, into different components. The crude oil is first heated in the fractioning column under normal air pressure. Different components of the crude oil have different boiling points ranging from 40°C to 360°C. The column is heated at different temperatures causing the liquid to turn into gas and pass into a condensing tube where it condenses into gas. The products are diesel, LPG, gasoline, petroleum, kerosene.

The waste material left is then passed into another column which is heated to 400°C under low air pressure. The low air pressure causes the melting point of the liquid to fall. The products then condenses out into a container.

Composition Natural Gas

Natural gas is a hydrocarbon. It is mostly composed of hydrogen, and carbon. Most of its component is the methane, CH4.

Sound Waves

Salam (May God Bless You). Sound waves are mechanical longitudinal waves which can travel only through a medium. Sound is more easily described as a disturbance in a medium, more commonly air. It has the same properties as any other wave, it can refract and it can reflect. A reflected sound is called an echoe. Its reflection and refraction is already discussed in my previous article Waves.

Sound Waves

Sound waves occurs when an object vibrates. The vibration of the object causes the air particles to vibrate as well causing the air particles to form rarefactions and compressions. A compression is an area in which particles are squashes together causing an area of high pressure. A rarefaction is an area in which particles are further apart from each other. This creates an area of low pressure. The wavelength of the wave is found by measuring the length from the middle of a compression to the other compression or from the middle of a rarefaction to the other rarefaction.

Pitch and Loudness

The pitch of a sound wave depends upon the frequency of a wave or more accurately the wavelength of the wave. The shorther the wavelength the higher the pitch and the longer the wavelength the smaller the pitch.

The loudness of a wave depends upon the amplitude of the sound wave. The longer the amplitude, the more loud the noise is and if the sound wave has a smaller amplitude, the sound will be much more quiet.

Harmonics

Different instruments tend to five different sound when playing the same note. Even if the frequency and the amplitude are same the sound will always be different. This is because these instruments produce a whole complex waveform. Each waveform contains a set of waves called harmonics or sometimes also known as an overtone (plural for harmonic). Each harmonic has different frequency, the first harmonic tends to have the lowest frequency and the frequency increases with the next harmonic.

Audible sounds

Humans can only hear sound waves which have the frequency of 20 Hz – 20,000 Hz. Human can not hear any frequency beyond or below that. This slowly decreases with age and also due to continouos exposure to loud noises.

Ultrasound and its uses

Sound waves with the frequency above 20,000 Hz is called ultrasound. Ultrasound has a lot of uses. One of its most common uses includes prenatal dioagnosis. A handheld device is used to emit ultrasound waves, these waves are then reflected back when it crosses the boundries between the different tissues of the mother and the fetus. The waves are then recepted by the device and then sent to the computer to form an image.

Other uses include, it is used to clean delicate objects. Once emitted, the dirt particles vibrate at the same rate as the air particles in the wave. This causes it to break down and fall. Other than that it is also used to find faults in building structures and other things. It uses the same basic principle, the waves are reflected when the waves touches the faults to the device to form images of the faults.

Electrolysis

Electrolytic Cell

A cell is better called an electrochemical cell. It acts as a pump which pumps electrons around a circuit it is connected in. Since electrons are negatively charged, the flow of electrons will always be from the negative terminal to the positive terminal.

If the cell is connected to a molten ionic compound then the charge will flow through the ions since no electrons are available. This cannot be applied to solid ionic compounds because the ions are in a crystel lattice and are not mobile.

In molten state or in aquous solution the ions become mobile and according to the kinetic particle theory have weaker forces of attraction between them causing the crystel lattice to derail or lose its shape.

An electrolytic cell is basically a container in which the process of electrolysis occurs. For electrolysis two electrodes are used which are connected to the oppositely charged terminal of a battery or cell. The other component is the electrolyte which is the substance needed for the process of electrolysis.

The electrode connected to the negative terminal is called the cathode and the ion which is attracted to the cathode is called the cation. It is attracted to the cathode because it is positively charged due to loss of electron and oppositely charged particles are attracted to each other.

The electrode connected to the positive terminal is called the anion which attracts the anion which are negatively charged due to gaining extra electrons.

One thing to notice here is that when anode forms ions, electrons which are produced are used to reduce the ions on cathode to atoms.

Two processes are commonly involved in this process. The oxidation and reduction. Oxidation happens when electrons are removed or oxygen is added into a substance. Reduction occurs due to gain in electrons or when oxygen is removed from the substance.

Electrolysis is easier to describe as the process which seperates a pair ions to form two atoms of different elemant. There are three main uses of electrolysis which are most commonly used in the industrial sector around the world.

Electroplating

Some things, like a spoon, are covered with seperate metals which make these kind of things more attractive and also makes it more lasting without any rust. To cover an object with a more valuable metal is called electroplating.

The object which needs to be electroplated is first dipped in acid to remove any traces of oxides. This object is then made the cathode and the metal needed to cover it is made the anode.

The electrolyte will be a soluble salt. At the anode metal ions will be formed and the electrons will be attracted to the cathode. The ions will then form atoms of the same metal on the cathode. Soon the object will be covered with the metal.

Purification of Copper

Copper is extracted from sulphide ores and is mainly extracted in impure form and must be purified. To purify it, it is first smelted and then turned into a copper ingot and is used as the anode. A small piece of pure copper ingot is used as the cathode and the copper (II) sulphide is used as the electrolyte.

When a charge is passed, at the anode copper is oxidized to copper ions: Cu → Cu(²+) + 2e(-). Simultaneously the copper ions are reduced to copper atoms at the cathode: Cu(²+) + 2e(-) → Cu.

The mass of the pure copper increases with time and the mass of impure copper decreases, the impurities in the impure copper are also gradually deposited at the bottom of the electrolytic cell. This way the copper is purified.

Aluminum extraction

Aluminum is extracted from the bauxite ore. Since this is an impure form of aluminum, it is smelted and through chemical reactions is turned into alumina which is the molten form of aluminum.

The alumina is then mixed in cryolite so that its melting point is decreased. The mixture is then poured in a Hall-Héroult, and then heated. Inert graphite electrodes are used in this case. At the cathode oxygen gas is given off which combines with the carbon (since graphite is an allotrope of carbon). This forms the carbon dioxide gas. The molten aluminum then seperates from the cryolite and then drains off.

At anode: 6O(²-) → 3O² + 12e(-).

At Cathode: 4Al(²-) + 12e(-) → 4Al

Hoffman Voltameter

Hoffman Voltameter is an expensive apparatus necessary to use for electrylosis if it results in formation of gases. For example, to electrolyse water, sulfuric acid is added in it and mixed because water is a covalent compound which does not have any ions. Inert platinum electrodes are used for electrolysis.

When the charge is passed, oxygen is produced at the anode and hydrogen gas is produced at the cathode:

At anode: 4OH(-) → O² + H2O.

At cathode: 4H(+) + 4e(-) → 2H².

A thing to know about this apparatus is that the term “voltameter” is not in any way linked to the word voltmeter, which is the device used to measure voltage in a circuit.

Pereferential Discharge

Pereferential discharge means that in the process of electrolysis some elements are discharged in preference to other elements. In these cases, the concentration of substances, the ease of discharge and the natures of electrodes matters. For example, a solution of sodium chloride has the ions; Na(+), Cl(-), H(+), OH(-).

Which ions are discharge at the cathode will depend upon the 3 factors written above. If Na(+) and H(+) is involved then H(+) will be discharged due to its ease of discharge. If Na is in higher concentration than H then Na will be discharged. The nature of the electrodes, whether inert or active, matters as well becuase if it is active, like in the case of copper anode and cathode, a different chemical reaction occurs than intended.

 

Electromagnetic Spectrum

Salam (May God Bless You). Today I have brought to you the article based upon the electromagnetic spectrum which consists of a 7 transverse waves. I will also briefly describe the applications of the waves known to be in the electromagnetic spectrum.

The Visible Light Spectrum

In 1686, Sir Isaac Newton placed a prism shaped glass block in front of sun light and determined that he could see almost 7 different colors.

If we observe, then the light coming from the sun or a lamp is a white light. This white light tends to disperse into the 7 different colors.

This dispersion is due to refraction of the light. Why this happens is because the white light is an electromagnetic wave and thus have the property of a wave, it seems to have various wavelengths.

Because of having different wavelengths, each wave refracts at different rates, this causes the beam of light to seperate into 7 separate beams of light.

In a rectangular glass block the light beams tend to refract back together when it exits the block but the geometry of a prism causes the light beams to refract more.

The red light refracts the least while the voilet ray of light refracts the most compared to other light beams.

A point to note is that there is no gap or a clear boundry between these rays of light which is why this is called a continuous spectrum.

You should know that the red light has a longer wavelength while the voilet light has the smallest wavelength compared to others.

These waves travel at the same speed in air and in a vacuume; 300 000 000 m/s, which is called the speed of light.

Since the speed is always the same, the increase in wavelength causes a decrease in frequency. The decrease in wavelngth causes an increase in frequency.

These wavelengths are so small that we use the term nanometer to measure the wavelengths of the waves. Fun Fact is that humans can only see 400 to 700 nm wavelengthsand those who cannot differentiate between these wavelengths are called colorblind.

To test this we use the equation mentioned in previous articles; v = fλ. You will notice the result as you calculate.

Electromagnetic Spectrum

The electromagnetic spectrum consists of the electromagnetic waves which are transverse waves.

These are emitted by the sun. Part of these series are; Gamma rays, X-rays, Ultra-voilet, Visible Light, Infra-red, Microwaves, Radiowaves.

The rays of light are also in a continuous spectrum as in the case of visible light. The Gamma ray has the shortest wavelength but the highest frequency while the radiowaves have the longest wavelength but have shortest frequency.

These waves also travel at the same speed, the speed of light.

The energy each wave can transfer depends upon the wavelength and the frequency of the wave. A short wavelength can transfer more energy than those with a longer wavelength and a wave with higher frequency can transfer more energy while the waves with shorter frequency cannot transfer much energy.

The Gamma Rays can transfer more energy than any other wave in the spectrum while the radio waves transfer far less energy.

The word Ultra-voilet means “beyond voilet” meaning that the frequency of the waves on this side is higher than the voilet ray of light in the visible light. Infra-red means “below red” meaning that the frequency of these waves are lower than red.

Applications of The Electromagnetic spectrum

The electromagnetic spectrum has proved its uses over the years.

Gamma rays are emitted by the decay of radioactive nuclei. It is useful mainly in the medicinal sector, where these waves are used for different purposes. One of which is that the rays are used to make pictures or diagrams of organs because it penetrates the skin easily and can be detected. It is also used to treat cancer. These rays are very dangerous to living tissue which makes them excellent for killing cancerous cells. These rays are also used to detect cracks in metals of a building or an object where it is impossible to do so.

The X rays are also used in the medicinal sectore, these are also capable to penetrate human skin but are stopped at the bones which are much harder than human flesh. This is useful to make Xray diagrams of bones to detect injury.

The Ultra voilet rays are very harmful to living tissue. Most of it is reflected off the Earth’s Surface, but our bodies have a further protection in our skin. Our skin has a pigment called melanin which gives our skin its color. It absorbs the Ultravoilet rays and do not let them enter the flesh. The Ultra voilet rays are used in SunBeds to tan our skin, the waves causes our skin to produce more melanin.

Visible Light is very useful today, it is the very source of light in the darkness of night time and is also used in fiber optics to transfer large bits of data around.

The infra-red are rays emitted by a hot object. The hotter an object the more infra-red rays it will emit. These rays have small range of wavelengths and frequencies. It is used in many household applications such as alarm detectors which detect a change in heat energy which is detected by these rays. These rays are also used by your t.v remote which sends signals to the t.v, each button has its own frequency and a little difference in wavelength in the infra-red waves.

The Microwaves are not reflected or absorbed by the Earth’s atmosphere. This makes it useful for sending signals across the space, and to the sattelites.

Radio waves are reflected by the Earth’s atmosphere, this is why these are used in communications. The waves can travel over the horizon, to large distances making it useful for contacting someone across the country.

 

With this I end this Article.

Light Energy

Light is a form of energy which travels as an electromagnetic wave. We have already discussed the reflective properties of waves in the previous article about waves, light waves also reflect when they touch an opaque surface. We use light rays for this because these are easier to observe.

Reflection of Light

Light waves follow the same principle as any other wave. When a few parallel light waves strike a smooth, flat surface, it will change direction and move away from the surface, in parallel rays. This is the principle of reflection.

On a rough surface the light rays do reflect but they will be more scattered. The rays will not be parallel to each other.

If a light ray impacts on a plane mirror, which is opaque, then the light will reflect. An imaginary line is formed perpendicular to the surface of the mirror at the point where the ray touches the surface, this straight line is called the normal.

The ray moving towards the mirror is called the incident ray which is incident on the plane mirror and the ray moving away from the mirror is the reflected ray.

The angle formed between the incident ray and the normal is called the angle of incidence, i.

The angle formed between the reflected ray and the normal is called the angle of reflection, r.

The angle of incidence and the angle of reflection is always equal.

Images formed By reflection

When you place a candle in front of the mirror and then look towards the mirror you will be able to see an image of the candle.

An image can be either real or virtual. A virtual image cannot be projected on to a screen. If you place the same candle in front of the wall you will notice that no image is formed on the wall.

A real image can be projected on the a screen. If you place a projector in front of the wall, and add the tape, then turn on the projector, it will form an image on the wall.

To you, it will appear as if the image is coming from behind the mirror although it is not true. In a diagram, we will show the rays as dotted lines that form the image behind the mirror.

In a diagram, you have to create two rays of light and at the point where the two rays converge an image is formed. Since the image is not really behind the mirror we will say that the image is virtual.

The virtual image will be of the same size as the object from which the light rays are coming from and it will be inverted (it will be back to front) and also will be at the same distance from the mirror as the object.

Refraction of light

All waves can reflect and refract. The reason waves refract is because of the sudden change of speed. Light waves travel fastest in vacuum, while it travels in about the same speed in air as in vacuum.

When it enters another transparent medium or substance that is more dense than the medium light is originally travelling in, the light wave slows down and then changes its direction. This change in direction is called refraction.

If you place a transparent glass block on a platform and point a laser light on to it at an angle the light will refract.

You can create a normal here where the light touches the glass block. Measure the angle of incidence. In case of refraction, the angle of refraction is used, which is in  between the refracted ray and the normal.

A point to be noted is that when light enters a denser medium from a less dense medium, the angle of refraction will always be smaller than the angle of incidence.

When the light wave moves from more dense to a less dense medium, its angle of refraction will always be greater than the angle of incidence.

If the light ray is moving straight, perpendicular to the glass block surface, then it will not refract but pass through.

The refractive property depends upon the thickness or, more importantly, the refractive index, n, of the medium that light travels in.

The refractive index is the ratio of the sine of the angle of incidence to the sine of angle of refraction: n = sin i/sin r. This equation is called Snell’s Law which is named after the Dutch scientist Willebrord Snellius known mainly as Snell.

The refractive index of a medium determines the angle of refraction of the light ray. The higher the refractive index, the angle of refraction will always be smaller than the angle of incidence.

If the refractive index is low, then the angle of refraction will be larger than the angle of incidence.

Total internal reflection

When light enters a less dense medium it has a greater angle of refraction than angle of incidence. When the angle of incidence increases then so will the angle of refraction.

There comes a point when the angle of refraction becomes 90°. At this point the angle of incidence is called the critical angle.

If the critical angle is further increased then the light will obey the laws of reflection. This is because when the light refracts, there is still a small amount of light that is reflected of the surface of the denser medium.

The light at this point is completely reflected which is why this situation is called the total internal reflection.

To find the critical angle we use the equation, c=1/n. c represents critical angle, 1 represents the sine of angle of refraction because angle of refraction is always 90 and sin(90) is always equal to 1, n represents the refractive index.

Lenses

Lenses can either be concave or convex. These lenses have different refractive properties.

The convex lens tend to cause parallel rays of light to refract and converge at a certain point. The concave lens causes parallel rays of light to refract and diverge.

The point at which the lens converge, an image is formed, and this point is also known as the principle focus or focal point. The distance from between the focal point and the lens is called the focal length.

The image formed might be real or virtual depending upon the lens as well as the distance at which an object is placed. In a concave lens, the image formed is always virtual, because the image appears to be coming from across the lens.

We will make dotted lines to see the light converge at a certain point, even though this convergence is imaginary, this will still become a focal point.

 Ray diagrams

To understand this, we can also make a ray diagram. The y-axis of the ray diagram is the lens and the x-axis will be the principle axis.

If an object is placed in front of the lens, light rays will bounce off the object and enter the lens and then refract.

The point at which the light rays will pass through the principle axis, that point will be the principle focus or focal point.

The length from this point to the lens axis will be known as the focal length.  The image will always be formed below the principle axis if the image is real.

To construct the light beams on the diagram, make a light ray from the object to the lens axis parallel to the principle axis and then from the lens axis change its direction towards the principle axis.

Make another ray of light straight through the optical center (the point at which the principle axis and the lens axis meet). This ray of light will not refract at all.

You can also make a third ray of light on the diagram straight through the principle axis, it should touch the lens axis and then it will refract and move parallel to the principle axis.

Real Image formed on ray diagrams

The point at which these rays of light converge, an image is formed. Mark the length of this point to the principle axis and this will be the magnification of the image.

To find the magnification of the image formed we will divide the length of the image to the length of the object. With this we can say that magnification is the ratio of the height of the object to the height of the image; m = hi/ho. m is for magnification, hi is for height of image, ho is the height of object.

We can also find magnification by dividing the distance of the image from the lens to the distance of the object to the lens; m=v/u. v is for distance of image while u is for distance of object.

The height of the image formed will depend upon the distance of the object from the lens. If the object is at the focal point, the image formed will be of the same size as the object.

If the object moves away from the focal point the image will magnify. If the object moves away twice the focal length, the image will diminish.

Virtual Images formed from Lens

In a ray diagram, if you move the object closer to the convex lens, then the rays of light will refract but will not converge, to an observer the image formed will be at the back of the lens.

On the diagram we would draw dotted lines towards the back of the object to a point where the light rays will converge, here an image is formed, since this is the point where the light is seemingly coming from (it’s not actually) this will make a virtual image which is magnified.

A concave lens causes the parallel beam of light to diverge. Because the parallel beam of light diverges, straight dotted lines (to represent the imaginary rays of light) are drawn from the diverged rays to converge them on the left of the ray diagram above the principle axis.

The  point where the light converges, that point is where the virtual image is formed.

Waves

A wave is a disturbance that travels across the environment through a series of oscillations or vibrations. A wave transfers energy from one point to another. The  particles involved in it do not move from their position but do vibrate or oscillate. This oscillation forms the crests and troughs of the waves.

Types of waves

• Transverse waves are waves which oscillates perpendicular to the direction of the wave. The best example of this kind of wave is found in a pond when you throw a pebble in it. You can see a wave being produced by this action. This is a ripple wave. What this represents is that the particles of the water are not moving from their positions but vibrating, transferring their kinetic energy to the other particle. If you tie a rope to a wall and grab the other end and move it up and down continuously, you would see a wave produce on the rope while the rope itself does not move towards the wall even though the kinetic energy is being supplied to the wall.
• Longitudinal waves are those waves which have oscillations parallel to the direction of the wave. The best example of this kind of wave is if you attach a spring with a wall and then grab the other end and move the spring forward and backward continuously. You will notice a series of compression and rarefaction formed in the spring which are properties of the longitudinal wave.
• Electromagnetic waves are waves like light waves and radio waves etc. These waves can move through vacuum (empty space) as these oscillations are present in the electric and magnetic fields. All electromagnetic waves are transverse waves because they vibrate perpendicularly to the direction of the wave.
• Mechanical waves like the sound wave and ripple wave move through matter (medium). Mechanical waves can be transverse waves or longitudinal waves.

Defining Waves

Waves have few properties properties yet to be discussed.

• Amplitude is the height of a crest or the depth of a trough from the point of rest in a wave.
• Wavelength (λ) is the distance from one crest to the adjacent crest or the distance from one trough to the adjacent trough of the wave in a transverse wave. In a longitudinal wave the wavelength is calculated by measuring the distance from the middle of a compression to the adjacent middle of the compression or from the middle of the rarefaction to adjacent middle of the rarefaction.
• Frequency (ƒ) is the number of crests in a wave in 1 second or the number of troughs formed in 1 second.

To find the speed of a wave we can use the equation: v=ƒλ. v is for speed.

Wavefront

Wavefront is an imaginary straight line which joins all points which have the same vibration.

Reflection of waves

Waves tend to reflect when they touch a flat surface. The best example can be seen in ripple waves. If these waves touch a straight wall which is at an angle from the waves, the waves would then reflect to another direction. An imaginary straight line is made at an from the point at which the waves touch the wall, this is called the normal, the angle formed from the normal and the direction of the waves is called an angle of incidence. The angle formed from the normal and the point of reflection is called the angle of reflection.

Refraction of waves

Waves also refract just as well as reflect. The best example of refraction can be taken from the ripple waves. If a wave moves from deeper water to shallower water then the wave slows down and then refracts. This is because when the front part of the wave touches the shallower water it slows down, and then the rest of the wave follows up and slows down as well and this continues on while the wave refracts.

Reflection of Sound Wave

Like all waves sound also reflects. To prove this you should set up an apparatus as suggested. Place a hard flat surface. Place a clock with a wide tube reaching towards the flat surface. Then place another tube at the adjacent side of the other tube and listen through the tube. You should hear the clock ticking.

Refraction of Sound Waves

Sound waves tend to slow down in cold air and speed up in hot air meaning refraction happens in between the layers in the atmosphere. During day time the ground air becomes warmer while the air high up is colder which is why sound waves refract up wards. At night the air in ground is cold while the air high up is warmer causing the sound waves to refract downwards.

 

Thermal Properties of Matter

Latent Heat and Specific Latent Heat

Some solids turn into liquids when they are heated. This is because the rise in heat energy causes rise in internal energy of the particles of the solid which then vibrate to break the inter-molecular bonds between each particle. As the solid is heated its temperature rises, but when the solid starts to melt to convert into liquid, at that point the temperature remains constant. This is because the heat energy is used to break the inter molecular forces which attract the particles towards each other. This is the point at which the temperature neither falls nor rises. This sequence is known as Latent Heat of fusion, Lf. The same is for liquids. When a liquid starts to boil, its temperature rises and evaporation is at its highest. But when the liquid is on the brink to becoming a gas, its temperature remains constant as heat energy is again used to break the forces of attraction between the particles. After this sequence the liquid turns into gas. This sequence is called as latent heat of vaporization, Lv.

The true definition of latent heat will be according to its type:

The amount of energy needed to convert a solid to liquid and vice versa without any change in temperature is called latent heat of fusion.

and;

The amount of energy needed to convert a liquid into gas and vice versa without any change in temperature is called latent heat of vaporization.

To calculate the latent heat of fusion of an object we multiply the specific latent heat of fusion with the mass of the object; Lf = m x lf.

Lf is latent heat of fusion.

m is mass of the object.

lf is specific latent heat of fusion ( it is written in lower case)

The same equation goes for the latent heat of vaporization; Lv = m x lv.

The specific latent heat of fusion is the amount of energy needed to convert 1 kg mass of an object from solid to liquid without any change in temperature.

The specific latent heat of vaporization is the amount of energy needed to convert 1 kg mass of liquid into gas without any change in temperature.

Just remember that the symbol to express Power is Watt and 1 Watt is equal to 1 Joules. The Joules symbol is used to express the latent heat.

Finding Specific Latent Heat

The specific latent heat of fusion of a pure substance is found by providing energy to a pure solid and calculating the mass of the liquid formed. For example, a known mass of pure ice is placed in a funnel with a beaker under the funnel. When water starts to drop out of the funnel, the temperature of the ice can be taken 0°C. Then an electric heater is placed inside the crushed ice and a known amount of energy is provided. Since the heater is provided with electrical energy, it can be calculated efficiently. When the ice is completely converted into water then the mass of water is calculated using an electronic balance.

To find the Specific latent heat of vaporization we heat up a liquid with an electric heater and then find the mass lost from the initial mass of the liquid. For example; A beaker is placed on an electronic balance, it is filled with pure water and its mass is calculated excluding the tare value. An electric heater is placed and the substance is heated. Then we measure the loss of mass of the liquid over the amount of power used to heat the substance. Note that the loss of mass of the liquid is a gain in mass of gas, such as loss of 3g of liquid is an increase in 3 gram of gas.

Heat capacity and Specific Heat capacity

If you heat one iron block and one copper block, both having a mass of 5 grams then you will notice that one block heats up faster than the other. If you heat 2  blocks of copper, one having the mass of 5 grams while the other having 10 grams of mass, then again the same effect occurs. This shows that the heat capacity of an object depends upon the mass of an object and the material it is made of.

Heat capacity of an object is the amount of energy needed to raise the temperature of an object by 1 Kelvin or 1°C.

To calculate the Heat Capacity we use the equation; C = E/ΔQ

C is heat capacity.

E is total energy used.

ΔQ is change in temperature (initial temperature – end temperature). For Kelvin scale we use the symbol ΔΤ.

The specific heat capacity of an object is the amount of energy needed to raise the temperature of 1 kg of object by 1 K or 1°C. To find the Specific Heat Capacity of an object we use the equation; c = C/m or c = 1/m (E/ΔQ).

c is specific heat capacity which is always written in lower case.

m is mass of the object.

C is heat capacity.

Finding heat capacity

The heat capacity of a solid is found by placing an electric heater in the solid along with a thermometer. The initial temperature is calculated. The solid is then provided with an insulation to avoid any and loss of energy. The electric heater then provides the solid with a specific amount of energy. The rise in temperature is then calculated to find the heat capacity of the solid.

For finding the heat capacity of a liquid, the liquid is poured in a container and is capped with a copper calorimeter. The initial temperature is measured by a thermometer. Then the liquid is heated with an electric heater and then the rise in temperature is measured. The problem with this is that the copper calorimeter absorbs some of the energy causing a little problem with measuring heat capacity.

Thermal Expansion and Charles’ Law

Every substance expands when heated and contracts when cooled. In solids, metals are best at this because these are good conductors of heat. The heat energy causes the metals to expand. This is why metal bridges tend to have rollers on one of its end to allow the bridge to expand a bit. A bimetal strip has two different types of metals, with one that expands sooner than the other causing the strip to bend.

In liquids, these expand better than solids. In a flask filled with water and capped by a stopper with a hole in it, place your hand around it for several minutes and notice that a small amount of water comes out of it. This is because the hands heat up the water and it expands. Water has an unusual property. Once it cools down, it contracts slowly, but when reached to 4°C it expands again. This is thought to be due to the density of water. Due to this the water expands and allows marine life to live even if there is a sheet of ice on the surface of the water in colder environments.

Gases also expand with the rise of temperature and does so better than any solid or liquid. To test this, connect a flask filled with air to a U-tube with a dyed solution and then heat up the flask. Notice that the levels of the liquid change as the flask is heated.

When gases are cooled, the volume of the gases decrease gradually and when a gas is heated then the volume also increases. This is shown by the Charles’ Law.

And in accordance to the law we devise the equation; V ∝ T or V = constant x T

To find the constant = V/T

V is volume

T is total temperature

Materials and Bonding

Elements

Elements are the smallest substance a material is composed of, it cannot be broken down by physical techniques. There are 92 naturally occurring elements  found and there are some artificial ones as well. Elements are composed of atoms.

Atoms are the smallest part of a substance taking place in a chemical reaction. These atoms are further composed of three subatomic particles; neutron, proton, and electron.

The atoms may join to form larger molecules. Molecules are composed of 2 or more atoms bonded together. The number of atoms are stated by the atomic symbol of the element such as H2, O2, N2 etc.

Elements are written as a subscript of their name such as Hydrogen as H and Potassium as K. These are the symbols of their respective element. The symbols of metals are written in separate symbols even though the atoms of the metals do not exist as separate atoms.

Some atoms have a different symbol than their names such as sodium has the atomic symbol of Na, and potassium has the atomic symbol of K. This is because the atomic symbols are given after the Italian names of the elements.

Compounds and Mixtures

Compounds are pure substances made up of atoms of different elements. The compounds are not mixtures of elements, the compounds and mixtures have different properties.

Compounds cannot be separated by physical techniques while mixtures can. Compounds are also made by chemical processes compared to mixtures. Compounds are written as the combination of the atomic symbol of the elements such as Sodium Chloride has the atomic symbol NaCl. Mixtures are not given atomic symbols.

For example; if you mix iron filings with sulfur powder, this forms a mixture. Now this can be separated easily if you place a magnet over the mixture. The iron filings will separate from the sulfur powder. If the mixture is heated, it will soon turn red and then turn grey and form a compound called Iron Sulfide.

Forming Bonds

Bonds are formed between atoms to form compounds. Many atoms do not have full electronic configuration. To fill the shells with electrons the atoms tend to form bonds. This can be seen in the elements in Group VIII which are mostly gases. These gases are mainly nonreactive.

This is why they were first known as inert gases. But now many compounds have been found out of these gases and are now known as noble gases. This is because these gases have a full electronic configuration.

Due to having full electronic configuration these gases did not form any compound naturally as no bonding was needed. Although there is still no compound for helium and neon.

Bonding only involves the valence electrons in the outermost shell of the atom of an element while the outer/core electrons are not involved in bonding.

Ionic Bonding

Some elements gain a full electronic configuration by losing electrons and gaining electrons. The ionic bond is formed between an atom which wants to lose an electron and the atom which wants to gain them. The atom which loses the electrons gains a positive charge due to increased number of protons than electrons which produces a cation.

The atom that gains an electron has a negative charge because of increased number of electrons than protons. This forms an anion. These ions form a bond between themselves. This is the result of the electrostatic forces between the cation and the anion. This is why the ionic bonding is also known as electrovalent bonding.

Covalent Bonding

Covalent bonding is the sharing of electrons. Some elements form compounds this way mainly because the atoms can not produce sufficient energy for ionic bonding. This why these atoms form covalent bonds. These bonds are represented in words as Cl-Cl, O=O, N≡N etc. These bonds are a result of strong electrostatic forces between the valence electrons and the positively charge nuclei of the atom.

Formulae of Compounds

These bonds depend upon the number of electrons needed for a full electronic configuration. These bonds are also dependent upon the combining power of the atoms. The combining power is the amount of atoms an atom of an element can bond with. Such as magnesium has the combining power of 2 and will combine with 2 chlorine atoms to form magnesium chloride.

These bonds are mainly formed from between non metals or metals and nonmetals. Compounds cannot be formed between every element. In case a compounds has a metal in it, its atomic symbol will always be written first and the ending of the nonmetal will be written as “ide” such as oxygen will be written as oxide and chloride will be written as chloride.

Properties of Ionic Bonding

 Ionic compounds form a crystal lattice. This means that its structure is fixed in a definite shape. The ions have strong bonds between them which is why ionic compounds tend to have a very high melting and boiling point. The crystal lattice does not allow conductivity as a solid because the ions are not free to move. If the ionic compounds are melted or mixed in a solvent the ions can now move freely and therefore conduct electricity. The ionic compounds are also soluble in water but this does not mean that the soluble compounds are ionic compounds as many such compounds are not soluble in water.

Properties of covalent compounds

Covalent compounds mainly exist as small molecules of compounds. The covalent bonding has intra-molecular forces between them but these tend to have weaker inter-molecular bonds. As a consequence of this these bonds tend to have low boiling point and melting point. Covalent compounds do not have ions and therefore does not conduct electricity.

Many covalent compounds have larger macro-molecules which have large covalent bonds between them. Macromolecules have high melting and boiling points. Some examples are; Silicon dioxide, Silicon Carbide etc.

Diamond and Graphite

Diamond and graphite are allotropes of carbon. Allotropes are different structural forms composed of the same element in the same physical state. Diamonds are clear crystals which have covalent bonds between carbon atoms. Each carbon atom is bonded with 4 other carbon atom. Since every atom is set in bonding, there is no valence electron available to conduct electricity, thus it is an insulator. Other than that the diamond has a high refractive index causing the light to refract and brighten up.

Graphite is also composed of carbon. Each carbon atoms are bonded with 3 other carbon atoms. The atoms form a hexagon. There are valence electrons available in graphite causing it to be a semi conductor. Both diamond and graphite have a very high melting point but other wise each have different properties. Graphite has weak intermolecular bonds thus it can be used as a lubricant whether a solid or mixed in a solvent. It is also used in pencil which is not composed of lead at all. Graphite is comparatively softer material than diamond.

Metallic Bonding

Metallic bonds has a lattice of cations with a sea of electrons between them. The electrostatic forces between the valence electrons and the cations forms a very strong bond between the atoms. The valence electrons also result in the metal being a very good conductor.

Properties of metallic bonds

Metals have valence electrons between their bonds making it a good conductor of heat and electricity. The heat energy agitates the electrons which collide and transfer the heat energy to other ions. Metals are also malleable. The layers of ions tend to fall over each other as the metal is pulled apart.

 

Temperature

Heat and Temperature

Heat is a form of energy. It travels from hot body to a cold body. While temperature is the measurement of how hot or cold a body is. These two things are not same but are closely related. Heat energy travels from a hotter body to a colder one, as an object gains heat energy, its temperature rises gradually. When heat energy moves out of an object or a body, the temperature of such body will fall. To calculate the temperature we use various thermometers.

Fahrenheit and Celsius Scale

Many scales have been devised over the decades, and almost all of them are forgotten. The Fahrenheit is an old scale still used today although the centigrade scale is more commonly used. But even the centigrade scale is not as recognized as the Celsius scale, because it has been devised by the Swedish scientist Anders Celsius in the eighteenth century. The centigrade and the Celsius scale have little difference. The scale for Fahrenheit is °F. The scale for Centigrade and Celsius is °C.

Making a thermometer Scale

A thermometer scale is made by calculating the boiling point and the melting point of a pure substance. A pure substance is essential for this because impurities in a substance alters the boiling point and the melting point of the substance. These impurities lowers the melting point and raise the boiling point.

For measuring the melting point of a substance, use ice cubes and put them in a funnel over a beaker and place a thermometer in between the cubes. As the ice starts to melt, it will gain heat. Read the temperature and mark this as the melting point of the pure substance.

To measure the boiling point, pour pure water in a flask and heat it over a Bunsen burner. Fix the thermometer above the water and not in the water. The water will gain heat energy and will turn into steam. Read the temperature and mark this as its boiling point.

Kelvin

The Centigrade and the Celsius scale are not scientifically used as these are unreliable. Some substances have a temperature below 0 and so have to be written as negative numbers. This makes it useless and so a new scale had been devised called the Kelvin, by the physicist Lord Kelvin. For devising the scale, the lowest melting point was taken in Centigrade/Celsius which is thought to be -273°C. This value is taken to be 0 K in the Kelvin scale. This scale is not written in degrees because it is an SI unit of temperature. To convert a Centigrade/Calvin Scale into Kelvin or Kelvin into Celsius/Centigrade scale is a matter of adding or subtracting 273 from the readings:

Celsius reading + 273 = Kelvin

Celsius = Kelvin – 273

Liquid In Glass Thermometer

The liquid in glass thermometer is most commonly used in clinics. The liquid in glass thermometer has a few properties which is very helpful for measuring temperature. The glass which makes the body of the capillary tube is thick acting as a magnifying glass for easy reading of the measurements. The bore was first made of glass but commonly is made of metal since metals are good conductors of heat. The liquid inside the glass is either alcohol (ethanol) or mercury. Both have their disadvantages and advantages but mercury is more commonly used as it reacts to heat better than alcohol.

Electronic Thermometer

Electronic thermometers are rising in popularity because of their ease of use. These thermometers show temperature digitally and has probes inside it which help do its function. The heat conducted by the metallic bore produces a resistance which forms the electrical energy needed for the thermometer to do its function. These thermometers are cheap and are easy to use and read temperature.

Thermocouple thermometer

Thermocouple thermometers are not commonly used but are great to use for an electronic circuit and for measuring high temperatures. The thermometer has two wires made of different metals, both wires join at a junction out of the two junctions. The conduction produces a resistance which can be connected to an electrical device. The advantages for using this kind of thermometer is:

• It can measure huge amounts of temperature, such as 1800°C, depending on the metals used for wires.
• The thermometer can be used in an electronic circuit.
• The metals are good conductors which is why these are best suited for temperature measuring making thermocouple thermometer more responsive to temperature changes.
• The wire junctions can be made small to use it to measure in small spaces.

Thermochromic Thermometer

Thermochromic or Thermocolor thermometer is more simple to use and is used for household purposes, mainly to check the temperature of an ill person. The thermometer has liquid crystals in it which change color due to rise in temperature.

With this I end this article

 

 

 

Transfer of Thermal Energy

Thermal Energy is part of the Cambridge O-level syllabus. It is a pretty easy and basic chapter telling us about the ways in which Heat energy a.k.a thermal energy is transferred, which is mainly through conduction, convection and radiation.

Heat

Heat is mostly termed as energy. It is commonly said as thermal energy. Heat is transferred one way or another. This is because the heat energy tends to raise or lower the temperature of an object until the temperature of the substance is equal to that of its environment.

 For example, if you place a cup of hot tea in a room and keep it there without any change in the environment, the tea will soon loose its heat and become cold. Similarly, placing an ice cold drink in the room will result in the drink becoming warmer than before. This is because heat energy is transferred from a hot region to a colder region. Other than that, heat keeps on transferring until the temperature of the substance is equal to that of the room temperature. Heat is transferred by conduction, convection and radiation.

Conduction

According to the kinetic particle theory, heat energy is converted into kinetic energy by the particles of the three states of matter. The particles in solid do not move about their position as they are packed together in a matrix but these particles vibrate and jostle other particles until every particle has received the kinetic energy and changed the state of matter. This process is conduction.

Almost every object can conduct heat. Some are poor conductors of heat which are called thermal insulators. The objects that are better in conducting heat are called thermal conductors. Almost all metals are conductors.

Metals tend to be the best at conducting heat and electricity. This is because of their structure. A metal has ions in its long matrix of atoms and ions. There are some electrons in metals that are called delocalized or free because they are not held by an ion. These electrons move around the metal structure freely. When metals are heated, the particles do vibrate but the free electrons move around the matrix of ions and atoms, these electrons spread the heat energy across the metal causing the metal to heat up faster than non metals.

Convection

Convection is the process of heat transfer in liquids and gases. This is because the particles in liquid and gas have huge distances between each particle and are more free to move. In liquids and in gases convection currents are the main ways of transfer of heat energy.

In liquids, we can fill a beaker with water and place a solid dye in its bottom corner in the liquid. Heat up the beaker over the Bunsen burner and notice as the dye diffuses into the liquid. The dye moves up and slowly moves down again. This is because the bottom the beaker is heated, the liquid in that region gains heat energy and loses its density, therefore it travels to the upper region, where the temperature is still low. The water from the top moves down to the hot region and gains heat energy. This movement allows heat to be transferred to the whole liquid until the liquid starts to boil and change its state to gas.

In gas, the same happens as in the liquids. The best example is found by the land and sea breezes. During the day the sea heats up slowly and the land heats up quickly. The air above land, once heated, rises into the atmosphere. This rise creates a low pressure in the region causing the colder sea breezes to come and take its place until this also heats up and follows the cycle again and again. This forms the sea breeze

During the night time, the sea is slowly losing its heat while the land loses its heat much more quickly. This causes the air above land to cool down and create a high pressure region. The air above sea is hot and by the same principle, it will move towards the land and the cool air moves to the sea causing a land breeze.

Radiation

In space, the Sun and Earth are distance apart from each other and there is vacuum between the Earth and the Sun but heat is still transferred to the Earth. This is because heat is transferred in the form of infra-red rays along with other rays emitted by the Sun. These infra red rays have short wavelength and is absorbed by the Earth. The soil absorbs the rays and emits them back to the atmosphere. This time the rays have a longer wavelength. These rays are absorbed by the greenhouse gases. The rays are again send back to Earth causing the Earth to heat up. This maintains the temperature of the Earth.

This shows that heat is better radiated and absorbed by dark, and rough surfaces compared to shiny and smooth surfaces.

 

Atomic Structure

Subatomic particles

Atoms were considered to be the smallest particle a matter is composed of but this is not true. Atoms are composed of three subatomic particles; protons, neutrons and electrons. Electrons are negatively charged subatomic particles which are found in the shells of the atom. The neutrons and protons are found in the nucleus of the atoms. Protons have a positive charge while neutrons carry no charge. Since atoms are not charged particles, that means that the number of protons and electrons are same.

The mass of protons and neutrons are greater than electrons. If the mass of proton is 1 then the mass of electron is taken 0. Even though these two subatomic particles are different in masses they carry a same charge.

Neutrons make up the mass of an atom along with protons (not electrons since they are outside the nucleus). The only exception is hydrogen in which no neutron is found.

Proton number and Nucleon number

The number of protons found in a nucleus of the atom of an element, then that number is called its proton number/atomic number. Its symbol is Z.

The total mass of an atom build up by neutrons and protons make up the Nucleon number/Mass Number of the element. It is given the symbol A. 

The neutron number is the total number of neutrons in an atom of the element and is given the symbol N.

The atomic number and mass number can be written as a subscript by the side of the symbol of an element.

Ions are formed when

the atoms gain or lose electrons. Losing an electron causes the positive charge of the proton to overpower the negative charge causing the formation of cation while gaining electron forms an anion which is negatively charged due to the same principle.

Electronic Configuration

The electrons are found in the shells of the atom. There are 4 shells in total. The equation given to calculate the amount of electrons each shell can take is; 2n^2. “n” means the number of shells. The 1st shell only holds 2 electrons, which forms a duplet. The 2nd shell holds 8 electrons forming an octect. The 3rd can hold 18 and the fourth can hold up to 32. If these limits are crossed then the electrons are to be placed in the next shell. However calcium and potassium are free of such pattern because as their 3rd shells exceed 8 electrons it is placed in another shell.

The electronic configuration, is basically telling the amount of electrons in each shell in an element. This is given in a table by stating the number of electrons present with “,” in between without any space.

Isotopes

An element might have a constant number of protons and electrons but this is not true for neutrons. These neutrons make different masses of the same element causing the element to divide into smaller groups of the same element called isotopes. One example of isotope is chlorine. It has two masses. One type is 35 which is more common, exactly 75.77%. While the other is 37 which is 25% found. This gives rise to the two isotopes; chlorine-35 and chlorine-37. This is exactly the way every element is written to express its isotope, such as, carbon-12, carbon-13 etc.

Carbon-12 Scale

To ensure the consistency of an isotope, the isotope is compared to an ideal isotope which is normally carbon-12. This isotope is chosen because it is found in all the organic chemicals but not all the isotopes can be compared to this mass scale. So to ensure accuracy the isotopic mass of any element is compared to 1/12th that of the mass of carbon 12.

Relative atomic mass

The relative atomic mass shows the abundance of a mass and the mass of an atom. This is showed in the following equation:

mass1 x abundance/100 + mass2 x abundance/100

For chlorine we will use this equation. Using this equation tells us that the relative atomic mass of chlorine is 35.5. The equation could be altered just to cope with more isotopes of the same element.

Relative molecular mass

The relative molecular mass of an atom is the sum of the relative atomic masses of the atoms that build up the molecule. Atoms combine to form larger molecules of an element. To find the relative molecular mass we can just add the relative atomic masses of the atoms that make up the molecule:

Cl2 = 35.5 x 35.5 = 71

The above equation is the example of finding out the relative molecular mass of the chlorine molecule.

Relative Formula Mass

Ionic compounds are made of multiple elements so we use relative formula mass to find the mass of such compounds. Such as if you find the relative formula mass of NaCl (Sodium Chloride), you will find that it is 58.5 as Na (sodium)= 23 and Cl (chlorine) = 35.5 and 35.5 + 23 = 58.5.

Radioactive isotopes

Many isotopes are stable and will remain in the environment for several years. But there are some unstable or radioactive isotopes which break down into other elements. One example is carbon-14 which converts into nitrogen-14.

 

Kinetic Particle Theory

States of Matter

There are 3 states of matter; Solids, liquids and gases. We can observe these states in pure liquid water. The water is liquid in room temperature at standard atmospheric pressure. If the water is placed in a freezer with temperature below 0°C the water turns solid; into ice. If the water is boiled in a kettle, the resulting steam will be produced. The steam is better to be called water vapor. This is transparent but because it condenses, as it comes out of the kettle into the low temperature environment, it forms small clouds.

Each state of matter is different in property. These properties are clearly shown by their physical features. The states of matter are changed physically and not chemically.

Kinetic Particle Theory

Each matter has particles grouped together. Each particle has a similar mass and size. In solids, the particles are arranged close together and form a definite shape of a solid. They have a very strong force of attraction between them and have a low amount of kinetic energy. Although they lack large amount of kinetic energy, the particles still vibrate about their positions. The particles collide with each other to transfer or gain energy. This is the case with liquids and gases. This is the reason the solids:

• The solids cannot be poured off.
• The solids are not compressed easily.
• Most solids don’t change their shape.

Liquids have loosely packed particles. These particles are not completely free to move but they do have spaces between them. The particles have a greater kinetic energy than a solid and have weaker force of attraction between each particle compared to solids. The Liquids are:

• The liquids can be poured off.
• The liquids change their shape as they take the shape of its container.
• Liquids are not easily compressed like solids.

Gases have particles which are further apart from each other. These have very weak force attraction between each molecule and have a great amount of kinetic energy. This is why the particles move further apart from each other. Most gases are invisible while others are not. This explains that gases are:

• Gases can be poured off.
• Gases are easily compressed.
• Gases change there shape as they take the shape of its container.

Conversion between States of Matter

The states of matter can be converted. This revolves around melting, boiling, cooling and freezing. A solid is melted to form a liquid. The liquid is then heated to produce the gas water vapor. This is because the particles gain heat energy and convert it into kinetic energy. The kinetic energy is then used to vibrate about their position. This weakens the force of attraction between the particles causing the mass to change its state.

In case of cooling, lowering the temperature lowers the amount of heat energy converting into kinetic energy causing the particles to loose their energy. This causes the force of attraction between the particles to strengthen, which slowly forms a liquid and in turn a solid.

We can make a graph of these changes.

The graph clearly shows that as a solid is heated, its particles gradually convert the heat energy into kinetic energy from point A to point B and from Point B to point C, the solid is slowly melting. It is in a solid-liquid state. This shows that it takes some time to heat up. Then the solid completely turns into a liquid and the liquid also slowly raises its kinetic energy from point C to D. From point D to E the liquid is in a liquid-gas state, it is gradually turning into a gas. From E to F the temperature of gas is rising. If the gas is trapped in a container then the gas will continue to heat up, but if the gas is released to the atmosphere then the temperature will not increase as the gas particles are lost.

These changes in state also depend upon the purity of a substance. An impure substance may result in a lower melting point and a higher boiling point which can be harmful for experiments. This can also be used to learn the purity of a substance.

Evaporation

Evaporation is the conversion of liquid into gas below its boiling point. Evaporation can occur at any temperature below the boiling point, but the warmer the air the higher the rate of evaporation. A volatile liquid is an impure substance. If you pure any harmless volatile liquid, such as petrol, on your skin, it will quickly evaporate and the surface from which it is evaporated will remain cool.

Sublimation

Sublimation is the process of conversion of solid into gas(by warming) directly without turning into liquid. The process by which a gas is converted (by cooling) into solid is also called sublimation and this is a reversible process. Carbon Dioxide is a good example of this. Carbon dioxide is a gas which is cooled to become the dry ice. The dry ice is then sublimed to become Carbon Dioxide gas.

With that I end today’s article.

 

Energy

Salam (May Allah Bless You). Today I am bringing you guys something pretty basic but I will write down some equations necessary for not only exams but for some practical demonstrations.

Energy is ability to do work. It is not easy to define energy but this is the closest definition to it. There are various forms of energy which act differently. Such as there is; heat energy, light energy, gravitational potential energy, kinetic energy, sound energy, magnetic energy, electrical energy, nuclear energy etc.

Gravitational Potential Energy

If an object is raised above the ground and you let go of it, it will be pulled down to the ground by the force of gravity which attracts all objects. This supports the fact that the heavier an object is and the higher it is raised above the ground the greater the amount of gravitational potential energy it contains. When it falls to the ground, it loses its gravitational potential energy. This can be shown through the equation:

Ep = mgh ;  Gravitational potential energy = mass (m) x gravity (g) x height above ground (h).

The gravity will always be 10 N/kg because this is Earth’s gravitational force, although in exams its value will be given to you.

Chemical energy

Potential energy can be stored in some ways. One type of potential energy is chemical energy. Energy is stored and is slowly utilized when a group of atoms or molecules group together to convert the energy into other form. The energy can be utilized much more quickly depending on the source of energy, such as, a fossil fuel converts its chemical energy into heat energy very quickly when burned.

Kinetic Energy

Kinetic energy is all about movement. The greater the velocity of a moving object the greater kinetic energy it has. This can be shown by the equation:

Ek = 1/2 mv^2

M is the mass of the object which will be in Kg

V is velocity. As the equation shows, the kinetic energy of an object is the double of the velocity of the object. If the velocity doubles, the kinetic energy quadruples.

Energy conversion

In different cases, energy tends to be converted into different forms. One good example is that if you throw a ball into the sky, it will move far above ground, meaning it will gain a lot of gravitational potential energy. The kinetic energy will also rise at the beginning of the throw but as it rises the kinetic energy decreases as it is converted into the gravitational potential energy. Just as the kinetic energy is converted, the gravitational potential energy also starts to convert into kinetic energy slowly and it gradually falls until its velocity doubles.

The ball does tends to bounce as it touches the ground but each time it touches the ground, the height it gains while soaring into sky lessens during each bounce. This is because some of the energy is lost, also, friction with the gas molecules present in air causes the ball to slow down. If the ball did not lose any energy after each bounce it would keep on bouncing to the same height forever.

Energy transforms into another form. It is neither created nor destroyed. So energy tends to transform from one form to another. Some devices convert one form of  energy into 2 or 3 more forms. Such as a television, transforms electrical energy into sound, light and heat energy. Other devices convert energy into one form only, such as an iron converts electrical energy into heat energy only.

Efficiency

Efficiency is the amount of energy used excluding the amount of energy wasted. Nothing is a 100% efficient, therefore, many devices use only small amount of useful energy. Such as a bulb receiving 100 Joules (J) of energy, it converts only 10 J of it to light energy which is the only purpose of the bulb for providing light.  It converts 90 J of the energy to heat energy. This 90 J is wasted as heat energy is useless in the case of the bulb. We can calculate the efficiency of a device by using the equation;

Efficiency = Useful Energy x 100% / Total energy input.

Efficiency is mainly calculated in percentage. One thing that should be noted here is that the amount of energy input is the exactly equal to energy output. Since energy is not destroyed or broken down, the energy input equals the energy output, it doesn’t matter in which form or in how many number of forms is the input energy converted into, the output will remain equal to input.

Work

In science work means amount of force used to move an object. Such as a crane lifting up an object is actually working as it pulls the object upwards and around. But when the crane is stationary even though it is holding the object in mid-air, it is not working as the object is not being moved. Therefore the equation for work is;

W = F x s

W is work which is expressed in Joules (J)

F is force and will be expressed in Newtons (N)

s is the distance the object moved and is expressed in meters (m).

Power

Power is calculation of amount of work done during an interval of time. It is calculated by the equation;

P = W/t

W is work which is expressed as joules

t is time which is expressed as seconds

P is power which will be expressed in Watts

Sources of Energy

Energy is released from a source. This can be renewable and nonrenewable. Non renewable energy sources releases energy more quickly than renewable sources and runs out. Renewable sources, however, do not run out. These sources of energy are mainly used to generate electrical energy to power modern devices.

Non renewable resources

These include the fossil fuels, crude oil, coal and natural gas. These are combusted to releases heat energy and are more commonly used in thermal power stations which generate electricity from these fuels. The disadvantage for using fossil fuels are:

• Fossil Fuels are in limited amount and are being used up more than they can be formed by the Earth. These will run out. The world will have to adopt to other sources of energy which might not be much helpful as the fossil fuels are.
• Extracting fossil fuels though mining and quarrying results in damage to environment.
• Fossil Fuels release a lot pollutants into the air during combustion causing environmental problems such as greenhouse effect and acid rain.

Nuclear energy is developed from the source uranium. This is also a non renewable source of energy. It is not a fossil fuel. It will remain a very helpful source of energy for a long time, longer than fossil fuels, and also does not damages the environment unless such power stations are handled with carelessness. If such stations are to be dismantled during its last stages, it is very difficult as the radioactivity can spread across the environment damaging not only the environment but also the organisms passing though such radioactive zones.

Renewable sources

Renewable sources are wind, light, and water. The light from the sun are used to convert the light energy to electrical energy with the help of silicon chips in the solar panels. The dams and barriers formed on a river makes an artificial lake. The water flows through the pipes in the dams and turns the turbines forming electricity. The water is also used as a source of energy in tidal form of power generation. There is a barrier formed between two tides. The water from the higher tide is flowed through a pipe containing a turbine. The turbine is moved causing the electrical energy to be formed and the water flows into the lower tide. Wind mills are used for utilizing wind. The kinetic energy from wind moves the turbine from the wind mills producing electrical energy.

These forms of energy can be useful for powering a small area or a single house. But these also limit the amount of electrical energy produced.

Its advantages are:

• These sources will not run out.
• Generating electrical energy from such sources is cheaper than non-renewable sources.
• It causes little amount of damage to environment.

Disadvantages are:

• Wind and water sources are useless with low kinetic energy as they need to turn the turbines while the sunlight tends to be useful during day rather than at night.
• The sources formed are all dependent on nature. They are not available all the time.
• Some power utilizing techniques such as dams and barriers, are useless in countries where there are no fast flowing rivers.
• These not only use up land but also destroy the scenic beauty of the land. Suppose a 100 windmills are used to power half a city, this means it covers more land than needed. Instead of using up land, one nuclear power station can power just as much area as more than 1000s of windmills can.

Identification of Gases and Ions

Chromatography

Chromatography is the process of using a filter paper or any other absorbent paper to separate pigments. A filter paper’s bottom part is marked with pencil where an ink is stained just enough to concentrate its color on to the paper. The solvent is poured in a petri dish. The solvent might be water but ethanol is preferred due to its high rate of solubility. The paper is than placed vertically upwards in the dish. The solvent should not touch the ink as it will dissolve in the solvent. As the solvent moves up the paper, the different pigments will get dissolved with the solvent and move up the chromatography paper. As the solvent reaches the top of the paper the pigments of the ink will stop at a certain point. This is a good way of showing the amount of pigments in an ink. The separated pigments will then be called a chromatogram. You will need to measure the Rf value by the equation;

Rf = distance traveled by substance ÷ distance traveled by solvent

Identification of Ions

Ions are charged particles. They get positively charged when they lose electron but when they gain electron they get negatively charged. A positively charged ions are called cations and the negatively charged ions are called anions.

Cations

Cations can be discovered by using sodium hydroxide and aqueous ammonia solution.

• Ammonium ion – In a solution containing ammonium ions add dilute sodium hydroxide solution. This reaction will produce ammonia gas which has a pungent smell. This turns the moist red litmus paper blue.
• Copper (II) ion – In a solution containing copper (II) ions add dilute sodium hydroxide. This reaction will produce a light blue precipitate of copper (II) hydroxide, which will be insoluble in excess sodium hydroxide.

Aqueous ammonia can be added to form a light blue precipitate which will be soluble in excess aqueous ammonia to produce dark blue precipitate.

• Iron (II) ion – To a solution containing Iron (II) ion add sodium hydroxide or aqueous ammonia, which will produce a dirty green precipitate of iron (II) hydroxide, which is insoluble in excess of either of the reagents.
• Iron (III) ions – In such solutions add sodium hydroxide or aqueous ammonia, this reaction will produce red brown precipitate. The solution will be insoluble in excess of any of the reagents.
• Calcium ion – Add sodium hydroxide to such solutions and a white precipitate is formed. Aqueous ammonia is not used here.
• Aluminum ion – Add sodium hydroxide or aqueous ammonia. The reaction will produce a white precipitate. But the test with the sodium hydroxide leads to the solution becoming colorless in excess sodium hydroxide.
• Zinc Ion – Add sodium hydroxide or aqueous ammonia . The reaction gives off white precipitate. The test with aqueous ammonia produces a soluble precipitate which causes the solution to go colorless.

Anions

Anions use a variety of different reagents.

• Carbonate ion – A solution containing carbonate ions is mixed with hydrochloric acid which gives off carbon dioxide. In the presence of lime water the carbon dioxide gets absorbed by it causing it to turn milky or cloudy.
• Chloride ion –  Mix the following solution containing chloride ions with a few drops of nitric acid along with silver nitrate solution. A dense white precipitate is formed. This darkens in the presence of sunlight.
• Iodide ion – Add the few drops of nitric acid along with silver nitrate solution to produce bright yellow precipitate.
• Nitrate ions – Add sodium hydroxide to the solution containing nitrate ions along with aluminum powder. This reaction gives off ammonia gas which has a pungent smell and turns moist red litmus paper blue.
• Sulfate ions – Add few drops of nitric acid along with barium nitrate solution. This gives off a white precipitate.

For chloride ions, iodide ions and sulfate ions nitric acid is used to remove carbonate ions which gives off carbon dioxide which causes effervescing of the solution.

In the nitrate test the aluminum powder reduces the nitrate ions to ammonium ions which causes it to give off ammonia gas.

Identification of gases

Ammonia

Ammonia has the characteristic of a pungent smell. The ammonia gas is soluble in water and turns the water alkaline. This is why a red litmus paper is used moist. The ammonia makes the water alkaline causing the litmus paper to go blue.

Carbon dioxide

In case of carbon dioxide lime water is used. The lime water absorbs the carbon dioxide gas and turns milky or cloudy.

Chlorine

Chlorine mixes with water to form an acid. This is then tested with the blue litmus paper. The blue litmus paper is turned red but soon it looses its color as the chlorine also produces bleach in the reaction.

Hydrogen

Hydrogen is highly flammable. It is less dense than air and so is collected by upward delivery method in an inverted tube. In the presence of flame, the gas in the tube sparks and explodes creating “pop” sound.

Oxygen

This gas supports combustion and causes more rise in fire than air itself. A glowing splint is placed over a tube filled with oxygen gas. The gas will cause the glowing splint to catch fire.

Sulfur dioxide

Sulfur dioxide mixes with water to make an acid which can then be tested with a blue litmus paper which would then turn red. But more efficient method is by mixing the sulfur dioxide in acidic potassium manganet (VII). The purple precipitate will soon turn colorless.

Water

For water cobalt chloride paper is used. Water turns cobalt chloride from blue to pink. Water also turns anhydrous copper (II) sulfate from white to blue.

Experimental Chemistry #2

Metal and acid reactions

Metal and acid reactions and metal carbonate and acid reactions gives off gases which is why they are of particular interest.

Metal +acid = metal salt + hydrogen

Metal carbonate + acid = metal salt + carbon dioxide

These reactions are used for the calculation of the rate of reaction experiments. The rate of reaction is calculated by measuring the amount of gas produced or by measuring the amount of mass of the mixture lost during the experiment. The dilute acid is poured into the metal acid through the dropping funnel and then the reaction produces gas gradually. The gas passes into the delivery tube.

Collecting gases

Gases are passed into the delivery tube. The delivery tube then supplies the gas to a burette which would be filled with water and inverted, fixed into a trough of water with a beehive. The gas passes into the water and collects in the vacuum. This method is useful if the gas is not soluble in water and is not required dry.

The gas can also be passed into an empty jar. The gases are supplied to the jars by either upward delivery or downward delivery. The upward delivery is used to collect gases which are less dense than air, such as hydrogen and ammonia. The downward delivery method is useful for gases which are either denser than air or is equal in density to air.

Before collecting the gases, they are passed though the gas wash bottle. This is done because the gas may have some impurities which are dissolved in water and the gas needed is collected in the vacuum. Another reason can be that the gas can be need dry so the gas is passed through sulfuric acid.

Purification

A pure substance is the one which has only one type of substance in it and has a fixed boiling and melting temperature.

A mixture is a solution of different numbers of substances which does not have a fixed composition. The boiling point and the melting point all depend on the composition of the solution.

Mixtures are described as homologous mixture if the substance has the same state of matter. Such as Air is a homologous mixture as it has all gases. If a substance is all solid or all liquid or all gas it is described as a homologous gas.

A mixture which has substances of different state such as a solution containing liquid and solid both, it is described as a heterogeneous mixture. Blood is a heterogeneous mixture.

Evaporation

Evaporation is a useful method of separating solids from liquids. The molecules of liquids gain energy by rise in temperature and soon start to move away from each other and into the atmosphere. Evaporation occurs in any temperature which is warm but is at its highest rate when the air is warm. The liquid in a bowl evaporates and leaves behind solid which do not evaporate. This method is used to collect sea salt. The sea water is trapped in small lagoons and allowed to evaporate until the salt emerges.

Distillation

Distillation uses the process of evaporation. The mixture is poured into a flask. The flask is connected to a condenser which has a jacket of cold water around it. the flask is heated and the solute evaporates leaving behind the solvent. The water evaporates into water vapor. The water vapor condenses in the condenser and comes out as a liquid in another flask. This method is used on an industrial scale in parts of the world to produce fresh water out of sea water.

Separating Funnel

Liquids that do not dissolve or mix with each other are called immiscible liquids. These mixtures are poured into a separating funnel. This can be used to separate oil from water. Oil is less dense than water so it always ends up being above water. The water below the oil is allowed to pour out of the funnel while the oil remains in the separating funnel.

Fractional Distillation

Fractional distillation involves the same process except that the flask is connected to another tube before the gas reaches the condenser. The tube is called a fractionating column which has inert material in it like glass beads. This method is used for separating miscible liquids. This method is used on industrial scale in factories like an oil refinery. Crude oil has a 100 of substances in it which are mainly hydrocarbon. It is also used for production of ethanol.

Decantation

A mixture might have large particles of solid. With a little care the liquid is poured into another flask while the solid particles remain in the same flask.

Filtration

If the solid particles are smaller then the mixture is poured into a flask through a funnel with a filter paper in it. The liquid passes through the filter paper and the solid remains on the filter paper.

Centrifuge

A centrifuge spins around the test tubes containing mixtures of solid and liquids. The solid separates from the liquid. Then the solution can be decanted off the test tube.

Experimental Chemistry #1

Salam (May Allah Bless You). This article has information about the basic part of chemistry. This is going to be basic but we will slowly make our way up to the advanced Chemistry.

Mass

Mass is the amount of matter an object or any substance contains. The mass is expressed in the SI units of Kilogram (Kg) for large masses while for small masses gram (g) is used. For even smaller masses milligram (mg) may also be used. The mass of 1 Kg is equal to a 1000 grams will 1 gram is equal to a 1000 milligrams.

The mass is measured by a balance. There are 2 types of balance. One is the beam balance which has the measuring pan and a movable mass on the left hand side. A sample is placed on the pan and the moveable mass is allowed to move about horizontally. The scale is then read. The use of a beam balance requires skills of the user and is dependent on it for accurate results. It does not require a power source.

An electronic balance is more accurate than beam balance and uses a power source. This does not require skills of a person. It also has a tare function. The mass of a beaker or a container which has liquid in it is called a tare. This hinders the accuracy of measurement of mass of a liquid as the tare value adds to the mass of the substance in the measurement. The tare function is that the balance can execute this mass and only calculate the mass of the substance inside the container.

Volume

Volume is the amount of space a substance covers. Volume is expressed in SI units cubic decimeter (dm^3) for large volumes while for smaller volumes cubic centimeter (cm^3) is used. Cubic meter (m^3) is also used when measuring large volumes. Liter and milliliter are used sometimes but are not agreed SI units to be used for calculating volume so they are converted to cubic decimeter.

There are two types of apparatus used for measuring volumes. There are those apparatus which are used to calculate accurate measurements and there are those which are used to calculate approximate measurement. The beaker is used for approximate measurement of volume of substance but the burrete is used for accurate measurement. For measuring volumes of gas, the gas syringe is used while the burette can also be used for this purpose by inverting it in a container filled with water.

Time

Time is measured in minutes (m) and seconds (s) by using watch. A digital stopwatch is used for best measurements. Time is very important to ensure the accuracy of many experiments.

Temperature

Temperature is the measurement of the degree of hotness of the body. The SI unit for temperature is Kelvin but it is mostly measured in Celsius or Centigrade (C°). The Celsius/Centigrade can be converted to Kelvin and the Kelvin can also be converted to Celsius/Centigrade:

KELVIN = CELSIUS + 273        ,        CELSIUS/CENTIGRADE = KELVIN − 273

Temperature is measured by using a thermometer. The most commonly used thermometer is the liquid in glass thermometer which has either dyed alcohol in it or mercury is used. In case of alcohol the measurement is taken from the bottom of the meniscus. The mercury is used more commonly in thermometers because it reacts towards temperature more fast than alcohol.

The electronic digital thermometer has probes in it which can detect temperature change and gives a more accurate temperature. It is also very cheap.

With that I end this article.

 

Pressure

Pressure in Solids

All objects are pulled towards the Earth’s surface by gravity. This pulling force is called weight. The weight of an object is constant but it will not always exert same pressure. The pressure will only be exerted by the part of the object touching the ground. Such as in normal shoes the pressure is exerted on the ground through the shoes. The amount of area touching the ground is not big enough so greater pressure is exerted or you can say that the weight is spread out over the area of the boots touching the ground. The snow shoes which have a larger area touching the snow causes the exertion of low amount of pressure.

This can be indicating by smoothing out sand on a tray and place a brick on the sand. Place the brick on the sand by the side which has a smaller width or smaller area. Place another brick but this time place it by its side which has more area. Let the brick exert its own pressure and then pull it out. Notice which side had created its mark in more depth. It should be the one with smaller area.

If you press a nail on to a board, the nail will exert great pressure on the board as it has a very small area touching the ground. The same is the case in stiletto high heels.

This equation is used to find out the pressure of an object:

pressure = Force÷Area ;    p=F/A

It is measured in Pascals and is expressed by Newton per square meter; N/m^2. When surface in contact with the ground is small then it will be expressed by N/cm^2

Pressure In Liquids

Liquids take on the shape of its container so the pressure exerted by the liquid is dependent on the height of the liquid and the density of the liquid. Pressure in liquid is calculated by the equation:

p=ρgh ;   pressure in liquids = density x gravity x height

It is expressed by Kg/m^3 or Kilogram per cubic meter. It is also expressed as gram per cubic centimeter or g/cm^3.

The pressure on the surface of water is 1 atmosphere due to the weight of air in the atmosphere. The pressure increases every 10 meter in depth.

The pressure in liquids vary if they have different densities such as mercury has greater density then water and so will exert 13.59 times greater pressure than water. This difference in pressure can be found out by a using a U tube. In a U tube add water and oil in the following way as shown in picture. Measure the length of the oil and the water in the opposite of the oil and use their densities in the equation:

ρ x g x h = ρ x g x h ;  density x gravity x height = density x gravity height

Take one equation on the either side of the equal-to sign  as the equation for oil and the other for water. You can use this equation for finding out the density of the oil.

Pressure in Gas

The particles of gas are in a random state of motion and are distant from each other. They also collide with each other and exert a force on each other to move away from each other. If the air is contained in a jar the particles of the gas will collide with the walls of the jar. This forms a pressure. This can be tested by a manometer. The manometer is just like a U tube with a liquid in it. Air is blown into the manometer from one side and the pressure by the air particles causes the liquid to move down the tube on the side where air is blown but rises on the other side of the manometer.

Atmospheric pressure

Air is a homologous mixture of gases which is composed of different gases. These gases exert a pressure on the surface of the Earth. This pressure is mainly 100 000 Newton which can crush our body but our bodies have the exact amount of pressure as the atmospheric pressure. On a mountain, as the ground rises above sea level, the atmospheric pressure decreases. The atmospheric pressure is expressed in the units; Atmosphere (atm), Pascals and Kilopascals (Pa and kPa), and in millimeters. The atmospheric pressure is measured by a barometer. This is sometimes called a torricilian in respect to its inventor Torreceli. The barometer is filled with mercury and is placed inverted on a trough filled with mercury. The cylinder is stood still by the atmospheric pressure. Measure the column of the mercury to calculate the atmospheric pressure in millimeters. The atmospheric pressure is not constant and can change.

Pressure and Volume of gas

A gas’s pressure can be calculated if a manometer is connected to a container filled with a gas. If the gas particles have low volume in the large container then it’s pressure may be equal to atmospheric pressure. This causes the liquid in the legs of the manometer to not loosen its height. If the gas is present in large volume, it will exert more pressure than the atmospheric air and push the liquid down the leg causing a decrease in the height of the column of liquid in one leg of the manometer but increases the height of the column of liquid in the other leg.

The same happens when the original amount of gas particles are present in a very small container.

You can calculate the relationship of volume with pressure by the formula:

(pressure x volume) first conditions = (pressure x volume) second condition

This is also known as Boyle’s Law ans is written as p1v1 = p2v2

With this I conclude this article. Thank You for reading and take care.

 

 

Food Tests

Salam (May Allah Bless You). I am sorry guys I haven’t posted in a month and more but I was having my Cambridge Examination of   Biology and today was the last exam, so I can post now. Today I have brought to you the last part of   Biology for O-level Cambridge as the rest have been written. You can check those out on my homepage.

Starch Test

1. Add a spatula measure of  starch solution in boiling tube. To test with a food just crush, grind and ground the food in water.
2. Pour a few drops of   Iodine Solution and stir the mixture.
3. Notice the color of  the liquid change. The iodine solution is an orange colored solution which changes to Blue Black in the presence of   starch but in the absence of   starch it does not change color.

Reducing Sugar Test

1. Reducing Sugars are monosacharide carbohydrates, such as glucose. Pour a 5 cm^3 of   glucose solution in a boiling tube. To test with a food just crush, grind and ground the food in water.
2. Prepare a water bath using a bunsen burner, a beaker and fill the beaker with water. Stir the water to evenly distribute the heat.
3. Place the boiling tube in the water bath and pour a few drops of   Benedict’s Reagent.
4. Let the solution boil. Mix the content of   the boiling tube to ensure even distribution of   the reagent.
5. Notice the color change from blue to green to yellow to orange to red. The color changes according to the concentration of   the reducing sugar. Blue means no reducing sugar is present, green indicates traces of   the reducing sugar, yellow has a slightly positive result while orange and red show the most concentration of reducing sugar.

Fat test

1. To test with a food just crush, grind and ground the food in water. Add the food in a  dry boiling tube. You can use cheese or oil or any other lipid.
2. Add 3 cm^3 of   ethanol in the boiling tube.
3. Mix the contents and add 2 cm^3 water in the boiling tube and notice the bubbles forming.
4. You will notice that the solution emulsifies.

Protein Test

1. To test with a food just crush, grind and ground the food in water. Add the content in boiling tube. Use a boiled egg white as it contains the protein albumin.
2. Add 3cm^3 of   water and mix it  well.
3. Add a few drops of   biuret reagent and mix it well.
4. Notice the color change. The biuret reagent is blue in color but changes to lilac color/violet in the presence of   protein.

This marks the end of   Biology and from tomorrow I will write on Physics and Chemistry. The way these will be written is in the same pattern as before for maximum understanding. I will try my best to provide you with the best information with the easiest of   ways to understand. Thank You for viewing and take care.

 

Genetic Engineering

For many years artificial selection has been used to produce better quality animals and plants to provide better yield and better quality of meat, milk, vegetables, fruits, etc. But it has been 40 years since genetic engineering had started and has slowly become part of our lives. Genetic Engineering is the process of modifying a genome (the entire gene structure in a chromosome) of a particular organism by adding a gene from a different organism whether from same species or not. This modification is also know as genetic modification.

Genetic Engineering can be done by isolating and copying the gene of a donor and then merging it into the genome of the host. The newly formed DNA sequence is called recombinant DNA because it is a combined DNA strand of two different organisms. The organisms are then called Genetically Modified Organisms (GMO). The GMO can then produce new proteins. Genetic Engineering is commonly used in modifying bacteria. The most common example there is that bacteria are used in fermentation to produce human insulin to treat diabetics. Before this, insulin was extracted from animals which was different in structure compared to human insulin.

Genetic Engineering in Bacteria for Insulin

  Bacteria have a single chromosome strand and has a bunch of circular DNA structures called plasmids. These plasmids are a vector for genetic engineering because these are used in the process. A single plasmid is first isolated from the bacteria and is copied. Then a small part of the plasmid is cut off from it by the use of restriction endonucleases. Restriction endonucleases are also known as restriction enzymes. These enzymes cut off the part of the plasmid.

Then a human gene which has the genetic code for production of insulin is isolated, copied and cut off in the same manner, with the help of restriction enzymes. The gene is then merged with the plasmid structure with the help of DNA ligases which are also enzymes but act as a “glue”. The plasmid is then placed back into the bacteria. The bacteria is then fermented to produce insulin in large scale.

The reason bacteria are more commonly used is because the bacteria reproduce quickly and have a tendency to produce these proteins rather fast.

Other Methods of Genetic Engineering

Other uses of genetic engineering are:

• The virus bacteriophage attacks bacteria and latches on to it. It places its DNA inside the bacteria and produces more virus particles like itself. The bacteriophage is a vector for genetic engineering. We can genetically modify the virus so that it can genetically modify any bacteria we need.
• A bacterium called Agrobacterium tumafaciens latches on to plant and leaves some of its plasmids in the cells. We can use the bacteria as a vector for genetic engineering. The genetically modified bacteria will release its plasmids in to the cells and that part can be cut off and can be grown into a new GM plant by micropropagation.
• A special apparatus called the Gene Gun can be used. It contains really tiny gold pallets. Its particles are covered with DNA. The gold pallets are shot into the plant tissue. Then that part can be cut off and grown in micropropagation to produce a GM plant.

Environmental Effects

Genetic engineering is being used around the world commercially because it has a huge amount of advantageous prospects but some scientists disagree with the use of genetic engineering claiming that we have not thought the long term effects of genetic engineering. Some of the harmful effects have been observed.

One such was that GM crops were used to resist the affects of herbicides which could kill weeds. This was going just fine until the crops started to cross pollinate with the weeds. The next generation of “super weeds” were resistant to the herbicides which became a problem for the scientists. Now more advanced herbicides are needed to kill this “super weeds”.

Other then that some biotechnology companies are abusing the use of genetic engineering by using terminating gene to genetically modify the seeds of the crops. Once the crops ripen, their seeds cannot be used to grow another batch of the same crop plant. So the poor farmers have to buy new seeds from the company after each harvest.

Crops are also given genes for killing insects but once they cross pollinate the new generation will have the genes to kill non target insect which damages the biodiversity.

Effects on Health

Some scientists have argued that there are disadvantages of the use of genetic engineering to human health. Two of these are:

• The affects of Allergens on humans is due to the use of GM food. Allergens are chemicals that cause allergy such as hay fever. The GM food are likely to promote the affect of allergens or may even contain an allergen.
• The GM bacteria are tested with antibiotic resistance genes to make sure whether the recombinant DNA is merged or not. This causes the problem which is discussed in previous chapters. The bacteria may develop resistance towards that antibiotic which causes more problems for the scientists who need to produce a better antibiotic to treat the bacterial disease caused by that specific bacteria.

Other then that there are moral or ethical reasons why people are against genetic engineering but it is spreading across the world very fast and is going to be used in future more vastly.

Calculating Magnification

This is going to be a short blog. The most important thing for a biologist, and a science student is knowing how to calculate magnification. It is crucial for a practical exam and practical tests. This is even useful for those who are in the alternate to practical section. Calculating Magnification is necessary for questions which have pictures or diagrams in it.

If you have been given magnification in an exam or in case of a practical test, you know the magnification from the microscope and draw an exact copy of the structure you see before your eyes whether practically or on an exam paper (you will be asked to draw a diagram) you can calculate the magnification of your drawing by the use of a normal meter-rule, half meter-rule, or a normal scale. With the measuring apparatus you should measure the length of your drawing and the length of the picture given in exam, divide these two numbers and multiply them with the given magnification to find the magnification of your drawing. The formula is as follows:

magnification of drawing= magnification of photograph (given) × length of drawing ÷ length of photograph

Sometimes the exam question would demand the magnification of your drawing but would not give the magnification of the photograph in that case we would have to calculate the length of the photograph and the drawing in micrometer (µm). To know the length of an object in micrometer, you should know that 1 mm is equal to 1000 µm. In this case the formula will be:

Magnification of Drawing= length of drawing ÷ length of photograph

These two formulas are necessary to learn and use to be successful in calculating magnification in your biology exam and even in practical tests

Diabetes

Diabetes Mellitus

Diabetes Mellitus is a disease in which the concentration of glucose increases in the body exceeding the limitations of the body. This is a dangerous disease because if it is left untreated then the patient will develop many more diseases like heart disease, kidney failure and would have weak iris in the eye. The person soon starts to loose weight and will weaken and will fall into coma and die. There are several types of the disease but there are two main types of the disease:

• Type 1 develops in children. This is due to the pancreas not producing enough insulin. The insulin produced is not sufficient enough to reduce the level of glucose in the blood. This raises the blood glucose level and causes diabetes in children. Insulin is provided to the patient by injections regularly.
• Type 2 diabetes occurs mainly in adults. This is mainly due to poor diet and poor lifestyle. Overweight people are likely to develop diabetes. This is because poor diet leads to the insulin receptors in the cells of the liver and target organs unable to recognize the hormone which leads to diabetes. It can be treated with having a balanced diet and exercising which prevents it in the first place. In some cases the type 2 diabetes can also occur in people who have a family history with diabetes is likely to develop diabetes due to genes (This can be understood if you have read my previous posts about genes). Injections are only necessary in severe cases.

The symptoms for both types are same. The person with diabetes is likely to have high glucose level in his/her urine. Other then that the patient would have constant thirst. This is because the high glucose level stimulates the hypothalamus.

Treatment

With type 2 diabetes you should have a good balanced diet. If you are overweight then you should diet/fast and exercise. Rise in glucose concentration happens due to large amounts of carbohydrates in a diet. The patient must keep away from any source of rich amount of carbohydrates, such as bread and pizza and any other food with carbohydrates in it. Keeping a healthy lifestyle prevents diabetes in the first place, however due to the gene which causes diabetes we cannot do anything to prevent it but we can treat it. In case of type 1 diabetes and in severe cases of type 2 diabetes, insulin injections are necessary to be taken every day. We cannot take insulin as tablets because it is a protein and will be digested in the stomach. To determine the use of insulin patients should use the biosensor which uses a test strip to determine blood glucose concentration. The patient must pierce his/her skin and rub the blood on to the test strip and place it in the biosensor. The device is very accurate and will calculate the exact amount of glucose concentration. This determines whether a patient needs insulin injections or not. A patient will have to test this several times a day.

Due to advance in science, a new device is available to help a diabetic (a person with diabetes is called diabetic). This is the insulin pump. It is connected to a very tiny tube called canula which is inserted into the skin to supply insulin. The pump has a monitor on it which calculates blood glucose concentration. The patient can check his glucose concentration and can use the monitor to adjust the amount of insulin entering the blood stream, according to his diet and lifestyle.

Even though a patient might take injections but he/she will develop diseases such as heart disease, kidney failure, and weakening of the iris muscles in the eye. To prevent diabetes and other disease which are caused by our lifestyle we must exercise, be active and keep a good balanced diet.

 

Fermentation

Fermentation is the process used to manufacture antibiotics, foods and drinks. It mainly involves the use microorganisms. It is a modern and a very useful technique. This process is used commercially across the globe to ferment products such as yogurt, cheese, bread, beer and various other products.

Making Beer

Yeast is added on to a sugary juice, like the grape juice, in an airtight container. The cap is attached with an air trap which allows the carbon dioxide to exit the container and does not allow the oxygen to enter. The yeast respires anaerobically. Once there is excess ethanol in the container, the yeast cells die, forming the beer. This is then extracted and mixed.

Making Bread

Yeast is added into warm water and flour is added. The mixture is kneaded and put on rest. During this period it is cut off of air and the yeast respires anaerobically producing ethanol and carbon dioxide. Sugar may be added to provide it the nutrients it needs for respiring. The enzymes in the flour break down the glucose, which is the reducing sugar, and converts it into energy, ethanol and carbon dioxide. The carbon dioxide bubbles forming helps the dough to rise. When put in oven the bubbles rise and the ethanol evaporates. Once cooked, this forms the bread.

Fermentor

A fermentor is a cylinder which is used for fermentation of antibodies, foods and drinks. It is also called a bioreactor. The fermentor may also be called either a batch fermentor or an industrial fermentor depending on its use and its product. The fermentor has various tubes going into and out of it providing air and nutrients as well as acids and alkalis for maintaining pH. The cylinders are computerized and are maintained by the use of probes which are connected to the computers. The microorganism which is required for a specific product is placed in the fermentor in the bottom of a liquid called a broth. The solution is stirred by the stirrers which helps in fermentation. The following factors show how microorganisms are taken care of for producing higher yields of antibodies or food like cheese or yogurt:

• The fermentation process produces heat energy which raises the temperature. This could kill the microorganism present in the fermentor. To prevent this a water jacket is present around the fermentor which has cold water flowing through it. This maintains the temperature for the microorganism to grow and reproduce in which results in a higher yield.
• Acids and Alkalis are added in to the fermentor which maintains the pH level to the optimum value. The acids and alkalis are added through a specific tube.
• Filtered air is sent into the fermentor so that the microorganism present in it can respire aerobically and would grow and reproduce. The air is filtered so that any microorganism present in the air does not flow into the fermentor and contaminate the process.
• Nutrients are constantly provided to the bacteria so that it can respire and grow and reproduce efficiently.
• Temperature indicators and pH indicators are present in the fermentor which helps in finding out the pH and the temperature of the broth.
• The stirrers stirs the broth so that the microorganisms remain suspended in the nutrients and respire effectively and reproduce. If there were no stirrers, then the microorganisms would have remained in the bottom and be cut off of the nutrient. This also helps in maintain the temperature of the broth.
• After the products are produced it is sent through the outlet pipe and the microorganisms are cleared out. Steam is passed into the fermentor to sterilize it and the bioreactor is then again used.

All the above factors are necessary to maintain and are essential for the high yield. By this we mean that such as if a bacteria is used to produce an antibiotic then these factors are necessary to maintain so that the bacteria effectively grow and reproduce. If the process is perfect then this produces a higher yield of antibiotic.

Fermentation of Antibiotic

Antibiotics are fermented by the bioreactors. One of the famous antibiotics fermented is penicillin from the bacteria Penicillium. The process starts the same. The bacteria is kept in the fermentor for several days, probably more than 2 weeks! The conditions inside the bioreactors are kept constant for the best growth and reproduction of the bacteria. Once the bacteria is ready for harvesting, the bacteria is sent out of the bioreactor through the outlet pipe and the fluid, which the bacteria releases during the process, is collected. After a number of chemical processes the extracted penicillin is “cleaned” or “purified” from the waste products of the bacteria and is crystallized. The antibiotic can then be stored in a powder form.

Single Cell Proteins

Single cell proteins (SCPs) are artificial food which are formed from the microorganisms. The microorganisms are either genetically modified or are set in certain conditions so that it produces protein substances. These are used to form single cell proteins which are then used as food. This was intended to be used to end the scarcity of food. But today most of the single cell proteins are used to feed animals and only few are used to feed humans. The single cell proteins are rich in proteins and can be used to replace the use of meat in diet.

This is kind of an effective way of feeding people. This is because using natural meat means that this meat is produced from the food chain. By this I mean that the cow feeds on grass, the biomass is decreased as it travels into the cow, and when the meat from the cow is consumed by humans then the biomass is further decreased. The use of SCPs provide a lot of energy. This much energy is provided without the loss of biomass in the microorganisms.

MycoProtein

Mycoprotein is an example of single cell protein. “Myco” means “fungus” as in mycology. The mycoprotein can be used to feed humans instead of meat or chicken or even mutton. It has rich amount of proteins and minerals in it. However it is not fermented in a normal bioreactor. A special, long bioreactor is used which forms a loop around itself. This loop fermentor moves the broth around the bioreactor by the help of filtered air compressing into the bioreactor. The material harvested is odorless and colorless and tasteless. Flavorings and colors is added artificially to form its taste exactly like meat.

Ecological Cycles

Ecological cycles consist of mainly 2 cycles; the carbon cycle and the nitrogen cycle. These cycles are very important to know of. The reason for this is that nitrogen and carbon dioxide are in limited amounts and have to be reused again and again. Carbon dioxide is in low amounts in the atmosphere in the form of carbon dioxide, it is almost 0.04% in the atmosphere. Nitrogen is in very high amounts in the atmosphere, almost 78% of the atmosphere is filled with nitrogen. But the carbon is used by the plants in photosynthesis as the gas carbon dioxide and is send back into the atmosphere during respiration. This keeps the carbon content in the atmosphere constant. Even though nitrogen is in high amounts the it is not used by the plant. It is used in the form of nitrites and nitrates through the soil.

Carbon Cycle

Carbon dioxide is found in the atmosphere in low amounts. This is used by the plants in photosynthesis to synthesize carbohydrates and oxygen. The carbon dioxide is continuously sent back into the environment during respiration. Other then that the carbon is also the product of respiration in animals. When we breathe, the carbon dioxide is exhaled and is sent back into the environment. So is the case with microorganisms. The use of fossil fuels have been a disadvantage. The combustion of fossil fuels have added to the carbon cycle. These increase the amount of carbon dioxide in air.

Nitrogen Cycle

Nitrogen is not used by plants in the form of gas. It is used as ammonia, nitrites and nitrates in the soil and is taken up by the root. These are essential for growth. The cycle shows that the plants take up the nitrogen from the soil and then is transferred to the herbivore and the consumers along the food chain. When the organisms die they are decomposed by the microorganisms. These microorganisms release the nitrogen in the form ammonia ions. The nitrogen fixing bacteria in the roots of the leguminous plants “fix” the nitrogen in the atmosphere and convert it into ammonium ions which is used by the plants. Other then that the ammonium ions are converted into nitrates by the process of nitrification. This is carried out by the microorganisms called nitrifying bacteria.

Leguminous plants means plants which have seeds in it like pea pods. These have roots with legumes in it which act as a container for the bacteria. The bacteria uses the nitrogen in the atmosphere to covert it into ammonium ions.

Artificial Selection

Charles Darwin was heavily inspired by the artificial selection which had led him to the theory of natural selection. He noticed that pigeon breeding was a common hobby at that time and observed that breeding the pigeons led to the production of a genetically different pigeon, which led to pigeons with different phenotype. He concluded that given the time natural selection could produce the same results as it was a very slow process.

For ages farmers have tried to produce better yield of meat, milk, and crops. These farmers had started cross breeding for this desire. These cross breeding soon resulted in today’s domestic food. This cross breeding for better yield is called artificial selection, and in it humans choose the animals and plants for breeding to bring about evolution in them. This is also called selective breeding.

Artificial Selection in Plants

In growing crops, fruits and vegetables, farmers use artificial selection to produce better yield. There are a ton of examples of this. One such example is a carrot. Wild carrots lack minerals and nutrients and are pale. They also do not taste good. Farmers around the world had started to breed new species of carrots. First they had the carrot self pollinated and cross pollinated according to situations. After the new carrot was reproduced it was cross pollinated. This process was applied for quite a lot of time and today we have orange, rich in minerals and tasty sweet carrots. These carrots are called domestic for this reason and are bigger in size and shape compared to the wild carrots. Same is the case with the cabbage family. Many plants which are cabbage shaped like broccoli and cauliflower have been artificially selected from the same plant, Mustard Flower plant.

Artificial selection in Animals

Artificial selection in animals is a common practice. Farmers do this to produce better quality meat and fur and to produce more milk. The farm animals, like a cow and bull, are cross bred and a genetically unique animal is born. That animal is again cross bred to produce another genetically unique animals. This process keeps on happening which is why soon new unique animals are born which produce more milk and better quality fur and meat.

Natural Selection

Natural Selection is a theory which suggests the occurrence of evolution among organisms which help the future generations survive in the world. Evolution has been discusses and observed over the ages, since the time of the ancient Greeks and was first witnessed in the 20th century. The theory was first proposed by the British biologist Charles Darwin and is accepted even today even though he was unaware of chromosomes, gene and DNA or even allele!

Discontinuous Variation

Discontinuous variation is a type of genetic variation. It describes the variation in genes in particular characteristics or catagories. My previous posts have been about discontinuous variation such as blood type, height, flower color, leguminous or non legume plant etc. To make this elaborate, we can take a particular population and set it up in a bar graph and show how the population shows a genetic variation in a particular feature such as blood group.

Continuous Variation

Continuous variation shows us the variation in Geno-type of a particular population. The continuous variation is limited to show the variation to a low number of categories, such as height or color . The bar graph can be used for the continuous variation.

Natural Selection

Natural selection explains the process of evolution. This has been observed for ages. Evolution was most focused in the 20th century and the theory of natural selection was given by the famous biologist Charles Darwin. He made 3 observations and 2 deductions from these observations. These observations were:

• The populations across the planet reproduce rapidly and produce more offspring than needed to replace them.
• No matter how much over-population occurs, the amount of population is always stable i.e; the land still has a lot of space and does not fill up with people and animals.
• All species show genetic variation

After observing these three points he gave 2 deductions that:

• The population of different species need to struggle for obtaining food and shelter to survive. . He also deduced that an organism has to compete others for survival. They need to compete for food and for shelter. Those who survive get to reproduce in large amounts. Their next generation of organisms have a different habit and features as opposed to their parents which helps them to survive while those who do not survive will reproduce in small amounts and would soon perish. This gave way to the phrase “Struggle for Existence”
•  They need to adapt to their environment. They need to adapt to the temperature of the environment, the structure of the environment, and have to live in many different living conditions. Basically, they have to fit into an environment to survive and reproduce. This gives way to the phrase “Survival of the Fittest”. (“Fittest” does not mean strongest. It means those organisms who are more “fit” to live in an environment.)

These deductions were made when Charles Darwin was completely unaware of DNA structures and alleles. Although evolution is slow it is most effected by selection pressures. Selection pressures are environmental factors which lead to evolution. Some of these factors are:

• Disease
• Temperature
• food supply
• predation
• competition for nest
• light
• competition for finding a mate

Some examples of natural selection are the use of insecticides on insects and the use of drugs on microorganisms.

Microorganisms

Microorganisms like Penicilium are used to produce the antibiotic penicillin. When this was first used the results were spectacular and it was a great form of protection against bacterial diseases. Soon the bacteria’s genes were mutated. These mutated bacteria survived the effects of antibiotic and reproduced forming new bacteria species who have immunity against such antibiotics. Though evolution is a process of decades, the bacteria evolved rather quickly because the bacteria reproduces very quickly. Same is the case with Insects.

Insecticides

Insecticides like the DDT were used to kill pest and insects to protect the crops and produce higher crop yield. Soon the insects were mutated and they reproduced very quickly. The new generation produced had immunity against such insecticides.

Sickle Cell Anemia

Although the alleles for abnormal hemoglobin Hb^S Hb^S lead to death before the patient reaches maturity, people around the world are still affected by it, meaning this does not have selective disadvantage. It should be noticed that people who have sickle cell anemia are mainly found around the regions where malaria is common. Having a sickle cell allele produces protection against malaria. This has a selective advantage for those who are heterozygous with this allele.However, there are people in America, where Malaria is not common, with the disease mainly because they are of African descent.

Chromosome Mutation

As read in my previous article; genetic mutation, you should know that chromosome mutation is an error in cell division. By this we mean that during cell division the chromosomes in any one pair do not divide and remain intact. This results in one daughter cell lacking chromosome in its one pair while the other has one extra chromosome in one of its pair. This error is called chromosome mutation and results in abnormality.

One common example is the Down’s Syndrome. In this disease, during meiosis the chromosome do not divide and the pair 21 has one extra chromosome. The egg formed from meiosis has the abnormal chromosome number. When it is fertilized with a normal sperm, it results in a zygote having 47 chromosome number rather than 46 (the diploid number of chromosomes in human cells). The offspring born from this is abnormal; it has slow growth rate, facial features indicating abnormality, and low to moderate intelligence. The mutation is common in older woman who fail to produce a normal egg. This means a younger woman has a 1 in 1500 chance of producing an offspring with Down’s Syndrome while in old woman it is 1 in 100 chance that the offspring produced has Down’s Syndrome. The offspring born with Down’s Syndrome may not survive but with proper treatment and medications the child will survive and live for a long lifespan.

Genetic Mutation

Mutation:

DNA replicates itself in a complex process during mitosis and meiosis. However, when the DNA replication goes wrong and the gene changes, it produces an allele. This is why an allele is defined as the different forms of genes. This change in gene is called a genetic mutation.

Mutation also occurs in chromosomes. The change in the shape or the amount of chromosomes present is called chromosome mutation. This can cause abnormality.

Genetic mutation

Genetic Mutation is a random event and is not caused by a medium or a disease.If it occurs in a specific cell of the body like the muscle cells or any other kind, It can be harmful to a cell. If it is harmful the cell soon dies and the mutation does not effect the body of an organism. However, If the genetic mutation is not harmful enough, the cell will survive and will eventually divide, producing the cells with the same kind of mutation. This kind of mutation is called somatic mutation. This can also cause cancer.

Albinism

Albinism is a good example of genetic mutation. Every organism has a pigment in their skin called melanin. It is formed by an enzyme reaction formed from the alleles. In Albinism, due to the faulty gene, the enzyme cannot be produced which is why melanin might not be present. This causes the lack of pigmentation or color in skin, hair and eyes.

Lack of color in skin is very harmful. In small animals which falls prey to the predators, they lack the normal color of their skin and do not have the camouflage ability and fall prey to predators. In humans, albinism in skin is very harmful. It makes the patient vulnerable to the sun’s rays and will very well develop skin cancer. Patients with albinism do not live long enough to pass these genes on to the next generation.

Sickle Cell Anemia

Sickle cell anemia is another example of genetic mutation. It is a disease commonly found in sub-Saharan Areas of Africa and other places around the equator. The sickle cell anemia is a genetic mutation of the gene which has the genetic information for forming the protein hemoglobin. Once the mutation occurs the hemoglobin is formed in abnormal amounts. This stimulates the red blood cells to turn into sickle shaped. In this state the red blood cells become more fragile and carry less oxygen. The sickle shaped red blood cells are also destroyed by the spleen faster than the normal red blood cells. This causes anemia. Anemia is a disease in which the person is lacking a huge amount of red blood cells.

The allele of the normal person is written as Hb^A while those who have the mutated allele is Hb^S. A heterozygous human would be a carrier of the disease but does not show its symptoms in most humans. Those people who are homozygous will show symptoms of the disease. Thus the chart is as follows:

Hb^A Hb^A                Hb^A Hb^S                                        Hb^S Hb^S

Normal                       Carrier of the disease                     Sickle Cell Anemia

No symptoms            Symptoms are rarely shown        Symptoms are visible

       It is quite advantageous to heterozygous human with the disease because this gives them the protection against malaria. When the pathogen is released into the blood, the sickle shaped red blood cells burst because they are so fragile and so the pathogen cannot absorb oxygen from the hemoglobin of these cells for respiration. These people can reproduce and can produce offspring which are invulnerable against malaria. This also shows the example of natural selection.

The Circulatory System

The circulatory system consists of the heart, the arteries, the veins and the capillaries. It is about circulating blood across the body and then returning it back to the heart.

The heart pumps out blood through the aorta and into the arteries. As heart beats every second so the blood is pushed forward every second as well. The arteries have thick walls and have thick elastic muscles near the heart. This allows movement of blood without the arteries bursting. The blood vessels are made of endothelial cells and have thick, muscular and elastic walls. The arteries carry the blood to all parts of the body providing oxygen and food molecules to the cells and also proving hormones and excretory products such as urea.

The arteries branch out and form arterioles. These arterioles then branch out into smaller capillaries. The small size of the capillaries help in diffusion of the substances out of the vessels. The blood then travels through the venules and flow to the veins. The veins then return the blood back to the heart. The veins are different than arteries. The veins are a bit flat and have valves inside it which is shaped like half moon which is why it is called the semi lunar valves.

The veins carry de-oxygenated blood without any pressure which is why it runs smoothly. It does not have any strong muscular or elastic walls. The valves are present to prevent back flow of the blood. The movement of blood is supported by the skeletal muscles on the veins.

Double circulation system In Mammals:

In mammals there is a double circulation system of blood. The first being the pulmonary circulation. The pulmonary arteries extend from the heart to the lungs which then carries oxygen back to the heart through the pulmonary veins.

The heart then pumps oxygenated blood through the main circulatory system, the systemic circulation.

Lymphatic System:

There are another set of tubes called the lymph capillaries which collect the tissue fluid. This fluid is then called lymph. The lymph is then transported to the veins where it diffuses into the blood.

This forms the lymphatic system. This helps in keeping the blood composition stable. It also helps in keeping the amount of tissue fluid in the body constant and takes off excess and supplies back to the blood at the veins near the heart.

 

Coronary Heart Disease

Arteries which supply the heart with oxygen through the blood are called coronary arteries. When fatty substances are deposited on the endothelial wall of the coronary arteries, they reduce the amount of red blood cells passing through it. This causes the decrease in oxygen supply to the heart. This in turn causes a heart attack.

The fatty substances which are deposited on the blood vessels, in the lumen, which forms the atheroma which blocks the blood vessels. It also hardens it which results in chest pain, mainly after exercise, this state is called atherosclerosis. As the atheroma increases in size it blocks the vessels, the blood cells then start to clot. This is why the red blood cells do not pass through the vessels in this condition. The heart won’t receive any oxygen from the coronary artery and will stop for a brief second. This is called a heart attack. Mostly it is not severe but if it is then it can lead to death.

Causes and Control

• Genes- If a person has forefathers who had such a disease is likely to have this disease. There is nothing we can do to prevent this but we can treat it if the patient consults his doctor in time.
• Diet- A person who has too much fats in his diet is likely to suffer from such disease. Eating too much dairy products like cheese, meat, and other oily foods. We should eat a balanced diet to prevent the occurrence of such diseases.
• Smoking– Cigarettes have nicotine in it which results in it which results in higher blood pressure and higher heart rate. The carbon monoxide in it combines with the hemoglobin and does not allow the oxygen to be supplied to the body. Smoking is a very dangerous habit and is also the reason for cancer. Even though people who do not smoke can develop cancer and coronary heart disease but smoking can cause likelihood of a person developing cancer and coronary heart disease.
• High Blood pressure – constant high blood pressure is also known as hypertension. This results in lower supply of oxygen. The heart beats faster causing heart attack because it beats faster and is supplied with less oxygen. It is mainly due to high amount of salt in our diet or by smoking and many other habits. We should have a balanced diet and avoid the use of high amount of salt.

The ABO Blood Group System

Blood Groups

Antigens on the blood cells are used to group the blood type of a person. The antigens are proteins and are called chemical markers. There are two types of antigen; A and B, these two can form a new blood type called AB. In blood type O there is no antigen present. This causes the antigen A or B to be dominant over O. To show these groups on a grid you should use the symbol I^A, I^B, I^O. The genotypes would be shown as such:

Geno-type                                   Blood Group

I^A I^A or I^A I^O                       A

I^B I^B or I^B I^O                       B

I^A I^B                                           AB

I^O I^O                                          O (No antigen)

In math the symbol “^” means powered by so there is no need to put this symbol just write the A, B and O in small size and in the upper right corner position.

Pedigrees

Pedigrees are like a tree of blood types in a family and can be used to easily display the blood type of all the family. It is as such:

The circle in a pedigree means female while the square is for male. It is fairly easy to use and if one genotype is missing, as if one can be missing from 3rd generation, you can deduces it by looking at the generation before it.

Determination of Gender in Humans

In a gamete of a human there are 23 chromosomes which is half of the chromosome number in a normal cell. Out of 23 chromosomes 22 are completely normal chromosomes and are called autosomes due to this reason. One chromosome of the gamete is different. It can be XX or XY depending on the gender of that particular person. In a male gamete, the chromosome is XY and in female it is XX. X means female while Y means male. This shows that if fertilization is to take place then there can be a 50% possibility that the baby born is male or female. The grid that is formed from this supports this possibility:

    X           X

X        XX        XX

Y        XY         XY

As the grid shows there is 50% chance that the off spring is a boy or a girl. The chromosomes of the gametes can also be shown in a Keryotype:

It is completely normal if a family has two boys and two girls and is not a slight bit unusual. Some parents might have one girl and two boys.

Organ Transplant

Antigens and organ transplant

Antigens are chemical markers found in all cells. It is different in every species. The antigens are used by the immunity system to recognize the cells of its own body and the cells from the outside environment such as the cells of a bacteria or virus. The antigens on the blood cells helps in identifying the blood type of a person. The most common known type of blood groups are A and B, which can combine to form new groups such as A, B, AB and O etc. However this can also come at a disadvantage when it comes to organ transplant. In case of blood transfusion, heart transplant, kidney transplant or any other kind of transplant, the immunity system recognizes the antigens on the cells of the organs as a foreign cell and produces antibodies against these organs and destroy the organ, this is called organ rejection.

To prevent organ rejection doctors take a specific organ from another person which has the same blood type. Normally the organ donor is chosen from the family of the patient which has the same blood type. If the family members are unable to provide their organ, such as kidney, then the doctors search for another organ donor with the same blood type as the patient. If such donor is found then immune-suppressant drugs are used to suppress the immunity system to prevent organ rejection. If the transplant is successful then the person would live for five or six more years (or even more).