Why does smoke go up the chimney?


    



          Smoke will rise up the chimney or through the nearest opening it can find because it is hotter and, therefore, lighter than the air in the room.



           Before the days of chimneys smoke was allowed to escape through vents or open turrets in the roof. Chimneys were introduced to induce a draught, thus providing more air for the fire. The hot smoke passing up the shaft made room for cool air, of higher density.



           Thus a chimney would not only carry away the smoke and gases from a fire but also act as a ventilator enabling a change of air in the room.











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What is fire?


           Fire is the outward sign that oxygen is combining with other substances in a spectacular chemical reaction. As the air is rich in oxygen, many materials will burn freely in a process scientifically called combustion, if their temperature is raised high enough. This explanation of what had been considered a mysterious phenomenon was discovered by the French chemist Antoine Lavoisier in 1783.



            The discovery of fire may have changed early man’s wandering mode of life to a more settled one because of an urge to keep the fire burning. It provided him with a new weapon for survival, warmed his cave and huts, enabled him to cook, and helped to scare off dangerous animals.



             In ancient time’s people in Persia, Egypt and India believed fire to be representative of the sun.








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What is dry ice?


               Dry ice is frozen carbon dioxide. When this gas is cooled to a temperature of -78.50C (-109.30 F) it becomes a solid without first becoming a liquid. This is why it is called dry ice. When frozen carbon dioxide is exposed to the air, it evaporates slowly as a gas without going through the melting stage in the way that ice made from water does.



              The fact that dry ice has a freezing point much lower than that of water makes it useful as a refrigerant, particularly for the storage of things that need to be kept very cold. When powdered dry ice is added to such liquids as acetone (used in the manufacture of chloroform) or ether, it is possible to produce a mixture which has a constant temperature of as little as -110o C (-166O F).




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How is Ink made?


               Ink is made from a pigment, or dye, and a liquid, called the vehicle, in which the dye is dissolved. 



              There are two chief types of ink: writing ink can be washable or permanent, and the ingredients used in its manufacture vary according to the colour wanted and the purpose for which it is needed.



               Blue-black inks are usually made from a dark-coloured solution and an extract of tannin. The dark solution is usually made from a soluble iron salt, such as ferrous sulphate. Blue dyes are added to blue-black inks to make it more attractive. Coloured inks contain other soluble dyes and the liquid vehicle is water. India ink is carbon black suspended in water and is usually used in drawing.



               Writing ink is made by purifying the water and then dissolving the other ingredients in it in large tanks. Afterwards the solution is clarified and then packaged in bottles.



               Printing inks are thicker than writing inks, often with a consistency like paint. The dyes are often dissolved in a heavy varnish.



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Why does iron go red when heated?


Iron goes red when heated because its atoms radiate vibratory waves of an electromagnetic nature that are visible as light as a sufficiently high temperature. At 8000 C the iron is at low-red heat. But as the heat increases the iron will turn bright red, and finally white-hot and molten.



      Heat is passed through the iron by conduction-the contact of one iron particle with another with no dependence on particle movement. The heat which is given off as light when iron glows red-hot can be reconverted into heat by the substance on to which it falls. When iron is heated to a temperature below 3000 C it gives off invisible rays of infra-red radiation which are similar in nature to light. But they do not contain quite enough energy per unit (photon) to stimulate the optic nerve and do be seen by the human eye.



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What is an aerosol?


An aerosol consists of fine particles of liquid or solid substances suspended in the air, or in any other gas. It is not, as many people think, merely a spray for use in applying paint easily, or getting rid of unpleasant smells.



      The germs of diseases, for example, are to be found suspended in the air, and these dangerous aerosols can be dealt with by spraying chemicals to form another aerosol which destroys the germs. Leaves of plants attacked by pests can be treated in the same way.



     Chemicals in the container part of an artificial aerosol spray are stored there under very high pressure. When the release trigger is pressed a valve opens, and the chemicals are forced out through a tiny hole in a fine spray. This invention is useful not only in the home, and to gardeners and doctors, but also to a wide variety of specialist users.



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When does copper turn green?


Although copper is highly resistant to the chemical action of the atmosphere and of sea water, it turns green if exposed to them for a long time. The colour is caused by the formation of a thin coating of green basic copper carbonate known as patina or verdigris. The latter name comes from the old French vert de Greece (green of Greece), but the reason for it is unknown. This beautiful green is often seen on copper roofs or statues, especially if they are near the sea.



     Copper was the first metal man learned to use. Five thousand years ago, when men discovered deposits of pure copper in what are now Iraq and Cyprus, they found that this fairly soft metal could be easily melted, cast in moulds and hammered into tools, weapons and ornaments.



      About half the copper produced today is used by the electrical industry. Pure copper is the best cheap conductor of electricity and can be drawn into threads one-thousandth of an inch thick.



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What is a glass made from?


Glass is made naturally from a fusion of silica (sand), soda and lime. This fusion can be achieved merely by lightning striking in a place where the right ingredients happen to be adjacent to each other. When glass is made by man, other ingredients are added, such as potash, lead oxide and boric oxide. Some of these ingredients are used to make glass clear, some to colour it, and others to give it a frosted effect.



      Glass was made by potters in Egypt for glazing stone beads as early as 12,000 B.C. As Egyptian culture progressed, craftsmen used glass for the manufacture of personal ornaments and bottles.



    A tremendous step forward in the use of glass was made by the Phoenicians in about 300 to 200 B.C. by the invention of the blow-pipe. The blowpipe is a hallow iron tube with a mouthpiece at one end and a knob shape at the other. The knob-shaped end is dipped into hot, viscous glass. A “gather” of molten glass can be blown by the worker into a hollow ball. The more he blows, the larger the ball.



    During the Roman civilization the art of glass-making reached near perfection. In the 3rd Century, the Romans cast glass on flat stones and produced the first window panes. The break-up of the Roman Empire and the ensuring Dark Ages brought an end to such cultural developments. The glazing of windows did not become wide spread over the whole of Europe until the 15th and 16th Centuries.



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Why does stainless steel resist rust?


Stainless steel resists rust because it contains a high proportion of chromium to carbon. Before the arrival of this alloy just before the First World War, Knives and other household articles made of steel easily rusted unless very carefully dried.



    It was an English researcher named Harry Brearley who discovered that rust was encouraged by the carbon in steel and other metals. The less carbon and the more chromium in steel, the better it would resist rust.



      But a careful balance had to be struck. Completely carbon-free steel was impossible to make, and only a limited amount of chromium could be included, because it tended to make steel brittle. Brearley discovered a satisfactionary formula only after many experiments.



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Why does an automobile have a carburetor?


An automobile is driven by an internal combustion engine which will work properly only if the right amounts of petrol and air are mixed together. The carburetor is the part of the engine where the mixing takes place.



     The burning of fuel in the engine is a chemical reaction in which petrol combines with the oxygen of the air to produce water, heat energy and oxides of carbon. A chemically correct mixture should have 15 parts of air to one part of petrol, both by weight. The amount of air then present is just sufficient to burn the petrol completely. If the engine uses a mixture with an excess of petrol a rich mixture-a small amount of unburnt petrol will be present in the exhaust fumes.



     A carburetor has to produce the required mixture to suit different engine conditions, such as starting, idling, acceleration, cruising and application of full power. It must be able to pass the correct mixture at all engine speeds and under varying loads, and has to atomize the petrol into tiny droplets and vaporize the resulting spray a combustible mixture.



     Inside the carburetor is a throttle valve which can increases or decreases the amount of mixture passing into the cylinders, which in turn control the power of the engine. This valve is mounted on a spindle which is operated by the accelerator pedal.



    A special device called a “strangler” or choke is also incorporated to help in starting the engine in cold weather by allowing an extra-rich mixture.



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What is plastic?


A plastic, in the modern sense of the word, is a synthetic or man-made material which can be formed into various shapes. The first plastic material was Celluloid, made in 1868 by an American, John W. Hyatt, by dissolving nitrocellulose under pressure.



      The use of plastic began slowly, but shortages of natural material caused by two world wars forced scientists to develop substitutes. Since the Second World War the making of plastics has become a gigantic industry, which has grown so fast that many people still have only a hazy idea what plastics are. In fact, the term “plastics” is as general as the word “metals”. The high-temperature cone of a rocket and the highly inflammable table-tennis ball are both plastics, just as lead and steel are both metals.



    However, all plastics have some things in common: first, they are entirely man-made and not found in nature; secondly, they consist of large molecules of an organic nature; thirdly, at some stage in their manufacture they are liquid and can be shaped; and fourthly, in their final state they are solid.



    Most of the raw materials for plastics are produced by the petroleum and coal industries. Scientists are able to produce different properties in plastics so that they can be used in a tremendous variety of articles.



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When does litmus paper turn Red?


Litmus paper turns red when placed in an acid solution, but blue is the solution is alkaline. This absorbent paper is the oldest and most commonly used indicator of the presence or absence of acid. Its special qualities are due to the fact that it has been soaked and impregnated with a mixture of dyes called litmus.



        The litmus mixture was originally produced by the action of air, ammonia and an alkali carbonate on certain lichens found in the Netherlands. It is now made from azolitmin and erythrolitmin.



     A litmus solution is sometimes used. But the message is the same. A few drops added to a liquid turn it red if it is acid and blue if it is alkaline.



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What is a detergent?


A detergent is substances which has a power to cleanse. This description applies to soap, as well as to soap, as well as to soapless shampoos and washing powders. A detergent usually has surface activating properties, which means that it is able to reduce the surface tension of water.



      In the process of cleaning the detergent acts as a bridge between the solid matter and the water. Soap molecules are shaped like tadpoles. The head is soluble, but the rod-like body is composed of an insoluble fatty substance. When mixed with water part of the soap tries to get away and the rest stays, thus breaking down the water’s surface tension. There is not sufficient room for all the soap molecules on the surface of the water. So they form bundles with the water-resisting rods on the inside. The dirt attracts the fatty part of the soap molecules which lift and surround it, while the soluble part of the molecules lifts and rinses the dirt away.



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Where does the wax go when a candle burns?


Nowhere- it simply changes into other substances. That is what burning does to everything.



       The moment you put a match to the wick, you start a change in the candle by turning the solid wax into a liquid. The liquid wax rises to the wick by an irresistible process called capillarity, the simplest example of which is the way blotting paper soaks up ink or water. Then the liquid wax changes into a gas which burns-a chemical reaction which releases energy in the form of light and heat.



     The presence of the gas can be demonstrated by blowing out the candle and immediately holding a lighted match an inch or so above the wick. The inflammable vapour instantly catches fire and the candle lights up again without the match having actually touched the wick.



     Other changes are taking place while the candle burns. The wax is a complex chemical compound of carbon and hydrogen. The process of burning is simply the combination of the wax with the oxygen in the air. If you put a jar over the candle, it will quickly use up the oxygen and go out.



Suring the time the candle burns, the carbon joins with the oxygen in the air and makes carbon monoxide and carbon dioxide, and the hydrogen combines with the oxygen to produce water.



    While all these changes in the substance of the candle are taking place, the candle, of course, is becoming shorter. But it is not “going” anywhere. Its materials are simply changing into other substances.



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Why do some liquids burn?


Some liquids will burn because when their molecules mix with the oxygen in the air the mixture becomes combustible.



       The application of heat promotes the necessary chemical re-action to put the molecules into more violent motion, so that they collide at high speed. The jolt loosens the bonds and makes it easier for the molecules to rearrange themselves and escape from the liquid to form a vapour, mixing with oxygen in the air.



       The most important liquid which will burn is crude mineral oil from which petrol and paraffin are produced. Others include tar and creosote, and the very explosive nitro-glycerin.



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