My Science School

        If you look through binoculars, you will find distant objects appear nearer and larger. Why does this happen?

        Binoculars are a pair of small telescopes built into a frame or casting. The two telescopes in binoculars are exactly similar in structure and meant for each eye. Each telescope is built into a funnel-shaped tube or cylinder. It consists of one objective lens and one eyepiece. The objective lens is kept towards the object and the eyepiece near the eye. The lenses are anti-reflection coated. Two prisms are also mounted between the objective lens and the eye piece to make the image of the object erect.

        The light from the object falls on the objective lens and an inverted image is produced by it. This image is further inverted by the two prisms, thus the image becomes erect. The eyepiece further magnifies this image. This is how we see the erect and magnified image of the object.

      

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In the early nineteenth century people believed that light travelled through imaginary stationary medium called ether. It was believed that ether filled all space, and all movements could be measured absolutely with respect to it. It was also thought that the speed of light relative to a moving observer could be calculated in the same way as the relative speeds of any two moving objects. For example, just imagine two cars in the same direction: one going at a speed of 110 km/hr and the other at 80 km/hr. Passengers in the slower car would observe that the faster car is travelling at 30 km/hr.

Two American scientists, Michaelson and Morley, experimentally tried to measure the speed of earth through ether in 1887. But their result did not confirm the existence of the hypothetical medium ether. Later the explanation of negative results was offered by Albert Einstein. According to him, nothing like ether exists in the universe and the concept of absolute motion is meaningless. He also said that the speed of light is constant, no matter how fast the observer is moving. No material body can travel faster than light.

On the basis of his conclusions, Einstein formulated the Special Theory of Relativity in 1905. He showed that physical quantities like mass, length and time are also not absolute. They change as the bodies move. If a body moves with a large velocity, its mass increases and it becomes shorter. 

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            Nylon is one of the most important chemical discoveries of the 20th century. It is one of the toughest, strongest and most elastic substances we have today. It is a synthetic plastic material which is made from chemicals derived from coal, water, air, petroleum, agricultural by-products and natural gas.

            It was first developed by a research team headed by a U.S. chemist Wallace H. Carothers working in E.I. Dupant de Nemours & Co. He began experimenting with it in the 1920s. In 1935, he produced the first piece of nylon. It was converted into cloth in 1937.

            Nylon is made from two chemical compounds: Hexamethylenediamine and Adipic acid. Hexamethylenediamine consists of carbon, nitrogen and hydrogen. Adipic acid contains carbon, hydrogen and oxygen. Each of these substances contains six carbon atoms and the nylon produced by them has been named as Nylon-6, 6. Manufacturers combine the two compounds to form a substance called nylon salt. A solution of nylon salt is placed in an autoclave (a heating device). The autoclave heats the solution under pressure. Water is removed and the small molecules in the compound combine to form large molecules. This process is called polymerization.

            When caprolactam is used as the starting material, Nylon -6, 6 is obtained. It has been so named because it has six carbon atoms in the basic unit. It is comparatively a recent development.

            In some factories, the newly made nylon comes out of the machines as a plastic ribbon. This is then cooled, and cut into small pieces. Nylon fibres are made by forcing molten nylon through tiny holes in a device called spinneret. The thin streams of nylon that come out of the spinneret harden into filaments when they come in contact with air. Then they are wound into bobbins. From a single bobbin, as many as 2520 filaments are united into a textile nylon yarn. The fibres are drawn or stretched after they cool. The stretching action causes molecules in the fibre to fall into straight lines and make the fibres stronger and more elastic.

            Nylon can be formed into fibres, bristles, sheets, rods, tubes and coatings. It can also he rendered into powdered form for making moulds.

            Nylon fibres resist mildew and not harmed by most kinds of oil, grease and household cleaning fluids. It absorbs little water.

            Nylon is used to make many articles of clothing, parachutes, carpets, ropes, fishing lines and upholstery. It is also used in tyres and bristles in many types of brushes. Solid pieces of nylon are used to make bearings, gears and small machine parts. Unlike metal parts nylon bearings and machine parts need little lubrication.

            Recently a nylon derivative known as Qiana has been developed. It is a silk-like fibre used in clothing. Thus nylon has proved to be useful in many ways.  

          You must have seen a crane lifting and moving heavy loads at construction sites and other places. The machine got its name from its resemblance to the crane bird which has a long neck!

          Although cranes have been in use .since ancient times, their widespread use only began in the 19th century with the development of steam engines, internal combustion engines and electric motors.

        Basically, cranes are of two types: fixed and mobile. The mobile cranes are more common. Some have a jib or boom that can move up and down and can swing around in a circle. Some others form a bridge and can lift a load up and down, move it along a track and move it from side to side above the construction site. 

          A common mobile crane is the crawler. It is mounted on a vehicle with wheels. These cranes are mainly used for civil engineering and construction work. They can lift heavy loads upto around 72 tons and can have a boom length of 30 m (100 ft) or more.

          Another type of crane is the hammer head or cantilever crane. It is used in the construction and erection of tall buildings. It has a long horizontal jib that is cantilevered and mounted on a tower. The tower can be raised by jacking it up, floor by floor, as the building becomes taller. The load is suspended from a trolley that moves along the jib. 

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          An automobile's speed is measured by a speedometer fitted next to the steering wheel of a car. It indicates the vehicle’s speed in kilometers per hour or miles per hour. The speed is read on the dial which is numbered from 0 to 160, by means of a pointer. Most speedometers also incorporate an odometer – a device that records the distance travelled by the vehicle.

          A speedometer is driven by a flexible cable that is connected to a set of gears in the vehicle’s transmission. When the vehicle moves, the gears turn a core or flexible metal shaft inside the cable. The core turns a magnet inside a metal drum called a speed cup. This is located inside the speedometer housing. The revolving magnet exerts a turning force on the speed cup. In turn the speed cup is held back from revolving freely with the magnet, by the opposing action of a hairspring. The movement of the speed cup is transferred to the pointer on the dial. The hairspring brings the pointer back to ‘zero’ when the vehicle stops moving. Most of the speedometers register 36 km/hr when the core inside the cable revolves at 1000 revolutions per minute.

          The odometer registers total kilometers travelled by the vehicle. Some automobiles also have Trip odometers that can be reset to ‘zero’ at the beginning of a particular trip. An odometer consists of a chain of gears (with a gear ratio of 1000 : 1) that causes a drum, graduated in 10th of a mile or kilometer, to make one turn per mile or kilometer. A series, commonly of six such drums, is arranged in such a way that one of the numerals on each drum is visible in a rectangular window. The drums are coupled so that 10 revolutions of the first cause one revolution of the second and so forth, the numbers appearing in the window represent the accumulated mileage.

Electricity is supplied to our homes, schools, factories and stores through copper or aluminium wires from power stations. These power stations burn coal or oil, use nuclear reactions or the energy of falling water to produce energy to run the generators. The power thus generated is then transmitted to different cities and places where it is required. Electricity is then transmitted through transmission lines.

To avoid the loss of power, the output voltage from the generator is first stepped up to a high voltage by a step-up transformer. After being received at the city power station, it is again reduced to low voltage, before it reaches our homes or factories. Now question arises how is electricity conducted through wires?

We know that all substances are made up of atoms. Materials which allow the passage of electricity are called conductors. Metals, such as copper, aluminium, silver and gold are good conductors of electricity. The atoms of these metals have loosely bonded electrons. These electrons are free to move within the metal. These are called free electrons and are responsible for the conduction of current. More the number of free electrons in the metal, better it conducts the electricity. 

When electric battery is connected across the ends of the metal wire, the negatively charged free electrons move away from the end connected to the negative terminals and flow toward the positive terminal. This flow of electrons is nothing but the electric current. Hence the drifting electrons cause electricity to flow. Greater the number of free electrons in a metal, easier it is for electricity to flow through it.

Some materials are poor conductors of electricity because they have less number of free electrons. Poor conductors resist the flow of electricity. The resistance of a wire depends upon its material length and area of its cross-section.

Some substances do not allow electricity to flow through them and are called insulators. These substances contain tightly-bonded electrons that cannot move away from atoms. Hence they do not conduct electricity. Glass, mica, wood, plastic and rubber are common insulators. Some substances like silicon and germanium are neither good conductors nor insulators. They are called semi-conductors. 

          An automobile such as a car is an automatic self-propelled vehicle. It runs on a gasoline, diesel or electric engine. Petrol or diesel engines used in automobiles are internal combustion engines. In these engines, fuel burns in the cylinder. In an electric engine, there is a motor and a gear box. It is battery-powered and used for small cars on a limited and experimental basis.

          Petrol engine is used in most automobiles. However, some automobiles even use diesel engines. Diesel engines are heavier and more expensive than gasoline engines, but they last longer and use less refined fuel.

         Both the petrol and diesel engines are four stroke engines. Their construction and working can be understood as follows:

Petrol Engine: It consists of a cylinder containing an air-tight piston. It is connected with the main shaft through a crank by means of a connecting rod. As the piston moves to and fro, its motion is converted into rotational motion of the crank shaft. The cylinder has two valves: one inlet valve and the other, exhaust or outlet valve. Inlet and outlet valves open and close automatically only once in every cycle. Air is mixed with petrol vapour in a carburetor and is made to pass into the cylinder through the inlet valve. The mixture is burnt in the upper portion by means of an electric spark provided by the spark plug. The action of the engine may be explained in four strokes.

          When the engine is made to work at the beginning by external force, the inlet valve opens and the mixture of petrol vapour and air is allowed into the cylinder. This is known as the charging stroke. Now both inlet and outlet valves close and the fuel mixture is compressed. This is known as compression stroke. The spark plug produces an electric spark and causes the mixture to burn. Due to combustion of the fuel, a large amount of heat is produced. This gives rise to heavy pressure and as a result the piston moves. With the movement of the piston the vehicle moves. This is known as the working or power stroke. Finally the exhaust valve opens, but the inlet valve remains closed. Unused gases, left at the end of the working stroke are thrown out. This is known as the exhaust stroke. In this way, one cycle is over. As the process is repeated, the vehicle goes on moving.

          Most automobile engines have four, six or eight cylinders. Most of the engines are in the front and drive the rear wheels. 

Continue reading "How does an automobile engine work? "

         A periscope is a very useful and interesting optical instrument. It enables officers aboard a submerged submarine to observe whatever might be happening on the surface. A submarine’s periscope can move up and down and turn to look in a complete circle. It allows tank commanders to view the battlefield from inside their armoured vehicles. It is therefore, useful in land and sea warfare. Now let us see what exactly a periscope is.

          A periscope is an optical instrument with which a person can see around corners and other obstructions. This instrument is based upon the principle of reflection of light from two parallel mirrors. A simple periscope consists of a long tube bent twice at right angles. Two plane mirrors, parallel to each other, are fixed in such a way, that the reflecting surfaces of the two mirrors make an angle of 45° with the axis of the tube. Rays coming from an object in front of the periscope, after undergoing two successive reflections, reach the eye of the observer thus enabling him to see the object.

         Some sophisticated periscopes also make use of reflecting prisms and magnifying optics, which make distant objects, appear closer. They are also fitted with devices for estimating the range of the target. Objects can be photographed through a periscope.

          Simple periscopes, made of cardboard, are also popular among spectators at parades and sporting events. With its help, they can see above people’s heads!

          Periscopes are also used in industry to observe nuclear reactions and the interiors of special furnaces and other dangerous devices.

          The longest periscope in the world measures 27 m. It is located at the National Reactor Testing in Idaho Falls, Idaho. It is used to view nuclear reactor operations.

          Wine is probably the first type of hard drink to have come into existence. Archaeological evidence suggests that wine making began in the middle-east over 10,000 years ago, and gradually spread westward to the mediterranean countries and finally into Europe. The ancient Egyptian wall paintings reveal that the art of wine making was known to them long before the Westerners took to it.

          Wine was common in everyday life of the early Greeks and Romans. It also played an important role in their religious ceremonies. The God of wine was called Bacchus by the Romans and Dionysus by the Greeks.

          Wine can be made from a wide range of fruits and vegetables, but the real wine is made from grapes. Grape juice contains water, sugar, fruit acids and many trace elements. The outer grape skin has millions of tiny living organisms, primarily yeasts, including a number of moulds and bacteria, too. 

          The grapes are allowed to ripen until they attain suitable sugar content (18% or more) and acidity. When these grapes are crushed, yeasts come into contact with the juice. This brings about the process of fermentation by which grape juice changes into alcohol and carbon dioxide. During fermentation, grape juice loses its sugar and turns into wine. This wine has 10 to 14% alcohol content. The rest of wine consists of water containing traces of acids, sugar and other substances which give the wine its colour and flavour.

          Another type of hard drink, beer, is known to have been made by the Egyptians and Babylonians at least 6000 years ago and there is evidence that barley, from which it is made, was cultivated in Britain and northern Europe, some 5000 years ago. Europeans knew how to produce a fermented drink from barley. Beer is usually made from barley hops, yeast and sugar by the process of fermentation.

          Pure brandy is made by the distillation of wine made from grape juice. The wine is heated and the alcohol that evaporates out of it is condensed and collected. Apart from alcohol, other substances are also given off during distillation. Some are poisonous substances and are removed.

          Different types of whisky are made from grains such as barley, rye and corn. Rum is made from molasses, syrup obtained from cane sugar. Gin is made from grain or molasses flavoured with juniper berries.

          Major wine-producing areas of the world include France, Germany, Spain, Portugal, Italy and California in the USA. 

            When a strip of wood, cardboard or waxed paper tipped with a chemical mixture is rubbed against a rough surface, the chemicals burst into a flame and produce fire. The first match was made in 1827 by an English pharmacist John Walker. It was a splint of wood tipped with antimony sulphide, potassium chlorate, gum arabic and starch. The match bursts into flames with a series of small explosions that showered the experimenter with sparks. The first safety match was invented in 1844 by a Swedish chemist Gustave E. Pasch. Let us discuss how matches are made?

            Red phosphorous is the main substance used in the match industry. Matches are mainly of two types: Lucifer or friction matches and Safety matches. 

            Lucifer or friction matches light when rubbed against any rough surface. The match is basically a wood splint or shaft about 8 cm long and 0.3 cm in diameter. It may have a tip of two colours, red and white or blue and white. One-fourth of the wooden strip is first dipped in molten sulphur or paraffin wax. The small white tip is made from the paste of phosphorous trisulphide. Other substances are antimony trisulphide (kindling material), potassium chlorate (supporter of combustion), powder of glass or silica (friction producing substance) and gum or glue (to act as a binder). Red or blue part of the tip does not ignite by rubbing, but burns when the white tip has caught fire. It carries the flame to the rest of the match stick. These matches are made by machines which produce millions of matches per hour.

            Nowadays only safety matches are used. Safety matches can only be ignited by striking them against a special surface. The surface is usually located on the sides of the match box. The tip of the safety match is made from the substances mentioned above except phosphorous trisulphide. Red phosphorous is used as the igniter in place of phosphorous trisulphide. When the head of the match stick moves over the rough surface, the molecules in the head and the surface collide with each other and the head of the match becomes hotter. The substances in the head become hot enough and make the head burst into a flame. These matches generally do not light when struck on any other surface. The chances of such a match stick catching fire accidentally are thus eliminated.

 

           We can measure our body temperature with a thermometer. Thermocouples and other devices are used to measure the temperature of furnaces. But how can we measure the temperature of stars?

          The surface temperature of stars is determined by various techniques. The most conventional and fairly accurate estimate can be made by colour alone. Red-coloured stars are cool while blue ones are extremely hot. On the basis of colour, stars have been classified in the table given below.

          A more accurate determination of the temperature is made by the comparison of spectra of stars. Light, which comes from the sun and other stars, is made up of many different wavelengths. It can be separated into different wavelengths by a spectrograph (an instrument used to record spectrum). From the spectroscopic studies, it has been observed that stars are largely composed of hydrogen (about 75% on the average). Next in abundance is helium followed by various other metals. In the cooler stars, some compounds are present but at high temperatures, they disintegrate into atoms. In order to know the temperature, the spectra of stars are recorded. It will be different for different stars, depending upon their temperature.

          Moreover, the intensity of spectral lines, bright or dark, varies with the temperature. It has been found that blue stars have O-type spectra; our sun has G-type spectra and so on. Blue stars emit 20 or more times the radiation per unit area than that of our sun does, whereas a red type may emit as little as 1/20 as much per unit area.

          From these spectra, by measuring and comparing the intensity of different lines and using Wien’s Displacement Law, the temperature may be determined. Intensity of emitted light is plotted against wavelength and the curve is drawn. The temperature of the star is directly proportional to the frequency at which most of its radiation is given off, i.e. to the highest point of the curve. 

                                                                                                                                                                                            

          A thermometer is an instrument used for measuring the temperature of our body or atmosphere. The first thermometer was produced by the Italian scientist, Galileo Galilei. Thermometers help in regulating chemical reactions by controlling temperatures of the solutions. They are used to measure the melting points of different solids, and boiling points of liquids.

          The main types of thermometers are: I. Liquid-in-glass thermometers. II. Bimetallic strip thermometers. III. Electrical thermometers. IV. Gas thermometers. 

Liquid-in-glass thermometers: The most common liquid-in-glass thermometer makes use of mercury or alcohol as thermometric liquid. The thermometer is made up of a glass tube with a narrow bore through it. At the bottom of the glass tube, a small bulb is blown, in which the liquid mercury or alcohol is kept. It is then put in a hot bath, as a result of which some of the liquid is expelled. The thermometer’s range is decided by the temperature of the bath. Finally its upper end is sealed.

          The sealed glass tube is now put in ice to mark the lower fixed point. This indicates the minimum temperature for the thermometer. Then it is put in another hot bath to ascertain the maximum temperature. The distance between the lower fixed point and the upper fixed point is divided into equal parts. When we wish to measure our body temperature, the thermometer is put into contact with the body. The thermometric liquid expands and stops when the temperature of the bulb becomes equal to the temperature of the body. The temperature is then read from the upper point of the liquid in the capillary.

          Clinical thermometers also contain mercury. Meteorologists use ‘maximum’ and ‘minimum’ thermometers to record the highest and lowest temperatures of the day. They contain both mercury and alcohol.

 Bimetallic strip thermometers: A bimetallic strip thermometer consists of a strip of two different metals having different co-efficients of expansion. This means that different metals expand unequally at the same temperature. The two metals used are usually brass and invar. Brass is an alloy of copper and zinc, while invar is an alloy of iron and nickel. The two strips are joined together. When the temperature changes, the two metals expand and contract at different rates. This causes the strip to bend. The strip is attached to a pointer which indicates the temperature. Bimetallic strip thermometers are used in refrigerators for temperature control. They are also used in thermographs. A thermograph records a graph of temperature. Instead of a pointer, a pen is attached to the bimetallic strip which records the temperature on a moving chart which is known as a thermogram. 

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            An acid is a chemical, which when dissolved in water, gives a solution containing hydrogen ions. Acids turn blue litmus red, they react with certain metals to release hydrogen, they react with bases to form salts and they promote certain chemical reactions.

            All acids taste sour. Fruits such as lemons taste sour because they contain citric acid. Vinegar is sour because it contains acetic acid.

            There are two main chemical groups of acids. They are organic and inorganic acids. Organic acids contain carbon while inorganic acids don’t. Some examples of inorganic acids are hydrochloric acid, nitric acid and sulphuric acid. They are also called mineral acids and they are very strong. Formic acid, acetic acid, etc are organic acids. They are weaker acids.

            Most of the organic acids are harmless. But inorganic acids can be dangerous as they can burn the skin. How do acids burn the body?

            Inorganic acids have a strong tendency to absorb water and release a lot of heat in the process. Since most of the living cells contain water, strong acids like hydrochloric, sulphuric and nitric acid react with them and kill the cells, causing severe burns.

            Acids are also essential for the body. Our stomachs contain hydrochloric acid to digest food. The stomach lining protects us from the acid, if the lining breaks; the acid can burn and cause an ulcer. Amino acids are essential for all kinds of life. Eight special amino acids are needed to stay alive.

            Acids also have tremendous industrial importance. Millions of tons of sulphuric acid is made every year and used for many industrial purposes. It dissolves rust and scale deposited on iron. Acids are also used in making fertilizers, pigments, dyes, plastics and synthetics. Aquaregia, which is a mixture of nitric and hydrochloric acid, is used to dissolve gold and platinum.

            Certain precautions are taken by people handling acids. They wear special clothes to protect their bodies’ from burns. Acids must always be poured slowly into water and never the other way round. If you are burnt by an acid, you should wash your skin with a lot of water, followed by a weak ammonia solution. If your eyes are affected, wash them immediately with water and then with sodium bicarbonate solution, which neutralizes any acid left.

 

        Dyes are colour substances which impart their colour to the fabrics on which they are applied and for which they have a chemical affinity.

          Until the middle of the last century, the only dyes available were natural products obtained mostly from plants and flowers. Their range was limited. These natural dyes included: woad, a blue dye obtained from the plant woad; indigo, another blue dye from a plant. Some other dyes such as madder (red) safflower and turmeric (yellow) were extracted from certain kinds of sea-snails.

          The most important breakthrough in this field was made in 1856 with the discovery of the first synthetic dye by William Henry Perkin. This was mauveine, a bluish-purple dye discovered accidentally by William Perkin during experiments aimed at synthesizing the drug quinine. After this discovery, efforts were made to develop dyes from coal tar. As a result of these efforts, several thousand dyes were synthesized subsequently.

          These synthetic dyes were satisfactory when used with animal fibres such as wool, but they were easily washed off from vegetable fibres like cotton. This difficulty was overcome by treating the fibres with metal salts or with solutions of these salts in tannic acid before dyeing.

          After these dyes a large number of azo dyes were developed. Azo dyes are two component dyes used for cellulose fibres. The material is first treated with one component, and then put in the solution of the other component. The two components react to produce a dye within the fibres themselves. These dyes are highly resistant to washing.

          Another group of very stable dyes used for cellulose fibres is known as Vat dyes. These dyes, which include synthetic indigo used for dyeing blue denim, are mixed with chemicals to make them soluble for the dyeing process. After the material has been dyed, it is treated with other chemicals to make it more stable.

          Today we have a large number of synthetic dyes obtained from coal tar or petroleum products which are not only used to colour textiles, but also plastics, paper, leather, fur, oil, rubber, soap, food, cosmetics, ink and metal surfaces. 

Man has been using soap and water as cleaning agents for thousands of years. The first soap was made in the middle east about 5000 years ago. The discovery of soap less detergents is not very old. The first synthetic detergent was not invented until 1916, but since then the manufacture of non - soap detergents became a major development of the petrochemical industry. New methods of fabric cleaning came into use, such as dry cleaning.

Dry cleaning is a method of cleaning fabrics with chemical solvents instead of soap and water. Many of these solvents are derivatives of crude oil. Petrol is the most important of them. Benzene is also used in dry cleaning. Their fumes can be dangerous if inhaled and they catch fire easily. Some safer synthetic chemicals such as polychloroalkanes and alkanes have also been developed. The most common dry cleaning chemicals are carbon tetrachloride and trichloro ethylene.

In a dry cleaning establishment, clothes are usually treated first for stains. Then they are placed in the dry-cleaning machine with the cleaning fluid or solvent and tumbled slowly for up to half an hour. After a rinse in clean fluid, the clothes are spun around rapidly to extract the liquid, and are finally fluffed in hot air. Any stains remaining are removed by hand and clothes and then steam pressed.

Dry cleaning has several advantages over ordinary soap cleaning. Cleaning fluids can dissolve stains (especially oil and grease) which soap and detergents cannot remove. The process is most useful for delicate or expensive silken and woollen fabrics because it does not have any undesirable effect on them. For instance, the colours do not fade, as they might in water.