My Science School

Pollution is a problem because man, in an increasingly populated and industrialized world, is upsetting the environment in which he lives. Many scientists maintain that one of man’s greatest errors has been to equate growth with advancement. Now “growth” industries are being looked on with suspicion in case their side effects damage the environment and disrupt the relationship of different forms of life.

       The growing population makes increasing demands on the world’s fixed supply of air, water and land. This rise in population is accompanied by the desire of more and more people for a better standard of living. Thus still greater demands for electricity, water and good result in an ever increasing amount of waste material to be disposed of.

    The problem has been causing increasing concern to living things and their environment. Many believe that man is not solving these problems quickly enough and that his selfish pursuit of possessions takes him past the point of no return before he fully appreciates the damage. It would then be too late to reverse the process.

    Ecologists say we are so determined to possess a new car or washing machine, or to obtain a greater yield from our crops by the use of fertilizers, that we ignore the fact that life depends on a lot of micro-organisms working efficiently.

     For example, if new chemicals were released into the environment, a combination of them might well poison one or more of the different type of bacteria in soil and water, which are essential to keep nitrogen being circulated from the air into organic material, and being cycled back into the air again. If this should happen on a world-wide scale, the air would become unbreathable.

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Fire extinguishers stop flames either by dousing them in water or by dousing them in water or by excluding the oxygen which a fire needs in order to burn.

     There are three main kinds of fires. First are those occurring in ordinary materials like paper and wood for which the quenching and cooling effects of water or water solutions are the most effective. Second come those involving inflammable liquids or greases for which a blanketing or smothering effect is essential. Finally there are the fires occurring in “live” electrical equipments where a special extinguishing agent must be used.

     The most common extinguisher for the first type of fire is a bucket of water, or a manufactured extinguisher with water containing a chemical. The chemical reaction expels the water which puts out the fire.

    For the second kind of fire the most common method is to use a chemical extinguisher to blanket the burning material, excluding oxygen and thus putting out the fire. When oil or grease is burning you should not use a foam-type extinguisher, as it may contain a certain amount of water. However these foam-type extinguishers are safe in most other cases, except electrical fires.

     For oil, grease or electrical fires a powder extinguisher must be used, never water or foam, as these could conduct electrical current.

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Hard water is water that contains certain dissolved chemicals that act on soap to form a scum. If water comes from limestone areas, some rock is dissolved in the water, and this makes it hard.

      There are several disadvantages in hard water. More soap or soap powder must be used to obtain a suitable lather. Also the scum clings to the object being washed. Hard water leaves a scaly deposit in kettles and boilers, which reduces the efficiency of both.

     But hard water can be treated to remove the unwanted chemicals. In the home small amounts of washing soda or borax can be added. At large water softening plants which serve a community, the water is filtered through a mineral called zeolite which removes the chemicals. After a time zeolite ceases to be effective, but it can be restored by washing it with salt water.

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An atom splits when it is struck by a neutron. The nucleus of the atom then breaks into two roughly equal parts and, at the same time, shoots out several high-speed neutrons.

      Atoms are so small that they cannot be seen under the most powerful microscope. They are the building bricks of which each element is composed. The Greek word “atom” means “cannot be cut”. But we know how that atoms can be cut, or split. Each one contains minute particle carrying two sorts of electricity: first the electrons which are negatively charged; and secondly, the central core or nucleus which is made up of protons (positively charged) and neutrons (no charge).

    In the 19th century it was discovered that all elements with atomic weights greater than 83 are radioactive and that the nucleus could be divided into several parts. Albert Einstein (1879-1955) calculated in 1905 that splitting an atom would destroy mass and release heat. By thus converting matter into heat energy, vast amounts of heat would be obtained by destroying only a very small amount of matter.

     Between 1934 and 1938 the Italian Enrico Fermi and the German Otto Hahn discovered that atoms of uranium (atomic weight 92) split when struck by a neutron. In 1939 Fredric Joliot-curie found that this splitting, or fission, released two or three more neutrons which in turn produced fission in more uranium nuclei, and so on. It is this chain reaction that makes possible not only the benefits of nuclear power but also the horrors of nuclear warfare.

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Some metals are chromium-plated to make them look more attractive and to make them look more attractive and to prevent them from corroding or rusting. Chromium is a silver-white, hard, brittle metal which was discovered in 1798 by N.L Vauquelin. Its non-corrosive, high-strength, heat-resistant characteristics are utilized in alloys and as an electroplated coating.

        In electroplating, the article to be plated is connected to the negative terminal of a battery and placed in a solution known as electrolyte. Direct electric current is introduced through the anode or positive terminal, which usually consists of the metal with which the article is to be coated. Metal slowly leaves the anode and forms a deposit on the article. The electrolyte for chromium contains chromic acid and sulphuric acid. It deposits a bright top layer but this is not the only important part of the electroplating. The chromium is only about 0.00002 inches thick. Under it lies a thick layer of nickel and beneath that again may be a layer of copper.

      Many household appliances are chromium-plated and so are the bright parts of an automobile. Tools, chemical equipment, electric appliances, gears, packing machinery, and hundreds of other articles are similarly treated to give them brightness, beauty or resistance to wear and rust. Electroplated and polished chromium is bright bluish-white with a reflecting power which is 77% that of silver

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He lead in exhaust fumes comes from the petrol used to drive the internal-combustion engine. Crude oil straight from the wells is thick, black and sticky. It has to go through a complicated refining process before it can be used as fuel for the engines of cars, Lorries, buses and aircraft.

        During refining, various substances are added to improve the petrol and for other reasons. For instance, small quantities of dye are put in to standardize the colour. Other substances prevent the formation of gum which would clog up parts of the engine.

     Lead in a liquid from called tetra-ethyl lead, is added to petrol to reduce “engine knock”. This means that it prevents the petrol from igniting in the engine at the wrong moment. When an internal combustion engine is running, the petrol is lit by sparks from the sparking plugs. The petrol burns in what is really a series of small explosions and produces gases which come out through the exhaust pipe as dirty, smelly fumes. And the lead comes with them.

They are also encouraging car manufacturers to design internal combustion engines which will work efficiently on lead-free petrol and have cleaner exhaust fumes. These engines will be more expensive at first, but they will help to make the air cleaner and pleasanter where there is a lot of traffic.

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Coal is basically a compound consisting largely of carbon. When a piece of carbon deep under-ground is subjected to great heat and pressure, it may gradually be transformed into a diamond. The heat turns the carbon into a liquid and the pressure causes it to crystallize.

       Thus the carbon loses its black unattractive appearance and becomes the most precious of stones.

     It has been calculated that this extraordinary process takes place at least 75 miles beneath the earth’s surface, the diamonds being afterwards transporated upwards by natural forces.

      Some iron meteorites full of carbon have been found to contain diamonds deep inside. Here the heat and pressure conditions would once have been much the same as those formed underground.

    Much the same conditions are created in the laboratory to make synthetic diamonds for industrial purposes, such as cutting hard materials. Only industrial diamonds are man-made. The diamonds that are considered the most precious stones in the world took thousands of years to form.

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       Flint is one of the various forms of silica, which is among the common materials making up the largest part of rocks. Some other forms of silica are quartz, opal, chalcedony, agate, jasper and onyx. Flint (essentially, silica with some water, a little lime, oxide of iron and, occasionally, carbon) can be grey, grayish-white, smoke-brown, brownish-black, red or yellow. It occurs as layers in other sedimentary rocks.

       Because it flakes and can easily be chipped into a sharp cutting edge, flint was used by prehistoric man to make axe heads, arrow heads, knives and other such sharp-edged implements.

        The study of implements from the Paleolithic, or Old Stone Age, and the Neolithic, or new Stone Age, has helped us understand how people lived them.

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