My Science School

             Drink-vending machines are operated electronically when coins are inserted and a button pressed to select the beverage required. They have four basic units, or a module on the inside of the cabinet door is the electrical unit where the dispensing of a drink is programmed through the other three-the cupper dispenser, the recirculating water system and the ingredient container units.

            When the coins are put into the slot, they are checked by an electronic scanning unit. If they are checked by an electronic scanning unit. If they are the wrong coins they are rejected. If accepted, they set off the programme.

               The release mechanism of the dispenser allows a cup to fall down a chute to the service position. While this is happening, a portion of the selected ingredient in powder from is released from its container into a large mixing bowl that looks like a big flattish funnel. Here hot water is added to dissolve the powder and the resulting beverage is poured into the waiting cup. Finally more water enters the mixing bowl, which is then automatically cleaned in readiness for the next customer.

             A car engine will stall-that is to say, it will suddenly stop when you do not want it to - if it is unable to provide sufficient power to overcome the load on the back wheels.

            This power is provided by the explosion of the petrol and air mixture pushing down on the pistons. If the load on the pistons from the crankshaft is exerting a greater force than that created by the explosion, the pistons will not move down the cylinder and the engine will stop. This can happen if the clutch is engaged too rapidly or if the hand brake is left on.

           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.

            The holes in a piece of bread are made by bubbles of gas. In bread-making flour and water are mixed to form dough. Then a small amount of yeast is added to the mixture. Yeast is a type of fungus which grows very quickly when it is warm an damp. While growing, it gives off a gas which bubbles up through the dough, making it expand. It is yeast which gives bread its particular flavor and appetizing  smell.

            No one knows when yeast was first used to make bread, but it must have been many thousands of years ago. According to one story, the idea was the result of an accident. Some yeast is said to have got into the dough by chance and made it rise. Because this loaf was twice as big as normal, people thought it must be magic. But as the bread tasted better than the usual flat, heavy loaves, they soon used yeast to make all their bread.

            Cakes also have holes in them made by bubbles of gas. But these are made by a different substance which leaves practically no flavor. This substance is baking-powder, which is a mixture of tartaric acid and bicarbonate of soda. When these two chemicals are mixed together, wetted and heated, they react to produce carbon dioxide. This gas bubbles through the cake mixture to make I rise while being baked.

            The first boat ever to be moved by steam power was designed by a Frenchman Jacques Perier and tested on the Seine in Paris in 1775. But the first really successful steamboat was built by Perier’s fellow countryman, the Marquis Claude de Jouffroyd’Abbans. His craft which was 141 feet long and equipped with straight-paddled side wheels travelled several hundred yards against the current on the Saone at   Lyons on July 25, 1783.

              Among early American pioneers was James Rumsey who in 1786 drove a boat at four miles an hour on the Potomac River, propelled by a jet of water pumped out at the stern. Between 1786 and 1790 John Fitch experimented in the Delaware River at Philadelphia with different methods of propulsion, including paddle wheels a screw propeller and steam-driven oars.

              The first to apply successfully the principle of steam to screw propellers was John Stevens whose boat, equipped with two propellers was John Stevens whose boat, equipped with two propellers, and crossed the Hudson River in 1804. However, his achievements was soon eclipsed by Robert Fulton’s 150-foot long paddle wheeler Clermont which in 1807 covered the 150 miles from New York to Albany in 30 hours at a maximum speed of five miles an hour. With Fulton in command on the Hudson, Stevens looked elsewhere, and in 1808 his new boat, the Phoenix, sailed out of New York harbor to become the first steamboat ever to go to sea.

              Both Stevens and Fulton were following in the steps of the Scottish inventor William Symington who in 1802 constructed a steamboat in Scotland, the Charlotte Dundas, which was used as a tug on the forth and Clyde Canal. The Charlotte Dundas was a paddle-wheel steamer used this method of propulsion.

           Industrial diamonds are used for such a wide variety of purposes that a sudden shortage would cause havoc in many branches of manufacture and mining. This is because diamonds, as well as being the most brilliant and precious of stones, are also one of the hardest materials known to man.

           Their earliest use in industry was as an abrasive powder for sawing and polishing operations and for grinding metal-cutting tools. Bort, which is the cheapest form of industrial diamond, is crushed into different grades for such purposes.

          Many kinds of arils use diamonds as cutters. The introduction of the carbonados or black diamond’s of Brazil-Less brittle than other forms-greatly improved rock drilling for geological and mine prospecting. But they have become so scarce that other suitable varieties have had to be substituted. Fine wires, like those needed for electric lamp filaments, are produced by pulling the metal through diamond drawing dies.

        Diamonds are also employed for cutting glass and porcelain, for fine engraving, for dental surgery, and for bearing in watches.

            Safety glass is glass that has been strengthened. There are two kinds of this protective glass-laminated and toughened-and both were discovered by accident.

             In the early 1900s EdouardBenedictus, a French chemist knocked a glass flask on to the floor. Although the glass starred and cracked, it did not break. After examining the flask he realized that a coating of dried celluloid on the inside had held the fragments together.

             Some years later, when injuries from broken car windscreens increased, Benedictus recalled this incident. Using glass sheets and celluloid bonded together in an old letter press, he produced the world’s first sheet of laminated, or layered, glass. Since then the clarity of the glass has been improved to equal that of ordinary glass. But it will withstand the impact of a half-pound steel ball dropped from a height of 16 feet. Toughened glass was developed later, although in the 17th century, Prince Rupert, nephew of king Charles I of England, discovered that molten glass was turned into immensely strong pear-shaped drops when tipped into cold water. Prince Ruport’s drops, as they are called, can be hammered on an anvil without breaking, but if the tail of the drop is broken they crumble into dust.

             In 1874 a French scientist, de la Bastie, heated small sheets of glass and then quenched them in oil, increasing their strength dramatically. However these sheets of toughened glass were very small and it was not until the 1930s that sheets large enough for use in cars could be toughened.

            Laminated or toughened safety glass is now used all over the world in cars, buses, trains, aircraft, ships and shops and has proved its safety value.

      Racing cars capable of moving at speeds well in excess of 100 m.p.h. need aerofoils to counter the effect of lift created by their highly streamlined shapes.

      Drag is caused by the turbulence of the air as it flows in to fill the vacuum left behind a forward moving object. The less streamlined the object, the greater the space to be filled in and the greater the turbulence. Therefore, the greater the “drag”.

       As designers improve the streamlining effect of racing cars to reduce drag, the cars’ shapes become more and more flattened and a new problem arises. The car has taken on similar properties to an aircraft wing and the movement of air over and under it at high speed begins to provide lift.

      The aerofoil placed at the rear of the car is so designed as to create a downward force when it passes through air at speed, and thus counteracts the lift. If this did not occur the cars’ wheels would make too little contact with the road surface and the driver would quickly loss control.

          The earliest wheels so far discovered were found in graves at Kish and Susa, two ancient Mesopotamian cities. These wheels are believed to date from 3,500 B.C. they were made from three planks, clamped together with copper clasps. This kind of wheel also existed in ancient times in Europe and the Near East. No one is sure where the wheel was invented, but this archaeological evidence suggests it was probably In ancient Mesopotamia

            A wheel with proper spokes was not invented until after 2,000 B.C. there are records of this wheel in northern Mesopotamia, central Turkey, and north-east Persia. By the 15th century B.C., spoked wheels were being used on chariots in Syria, Egypt, and the western Mediterranean.

           The solid wheel was used mostly in farming. Tripartite wheels- wheels with three spokes- were being used in the Bronze age in Denmark, Germany and Northern Italy for carts.

          The invention of the wheel made it possible for people to transport heavy objects much more easily. It also enabled them to travel farther and trade with each other more easily, and so find out about other countries and customs.

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          A firestorm occurs when flames from a large number of individual fires merge into a single convective, or circulatory, column. This produces so much heat that all the buildings below are set on fire. Firestorms cover a whole area, trapping the population within them.

          During the Second Worlds War enormous destruction was caused by fire in British, German and Japanese cities. In Britain and Germany the thousands of fires started by incendiary bombs usually burned individually, with relatively little spread between buildings. This was because of the materials from which the buildings were constructed, their size and the lay-out of the cities.

          However, in Japanese cities mostly made up of low wooden-framed houses the American bombing attacks brought about a number of annihilating firestorms. The most terrible of all was that caused by the atomic bomb dropped on Hiroshima, on August 6, 1945. This storm contributed in great measures to the death toll of 70,000 to 80,000 people. In the second atomic bomb attack on Nagasaki on August 9, 1945, fire damage was again severe.

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               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).

               The first ride able bicycle was made by Kirkpatrick Mac Milan of Dum-friesshire, Scotland, in 1839, although an attempt to construct one had been made by Jean Theson at Fontainebleau, France, in 1645.

               Before this, crude machines had been made, which had no farm o f steering and had to be propelled by publishing the feet against the ground. Machines of this type appear on bas-reliefs in Babylon and Egypt and on frescoes in Pompeii. In England, a stained glass window, dated 1580, in the church of Stoke Poges, Bucking hamshire shows a cherub astride such a machine.

               But all these machines seem to have been four-wheeled. The true bicycle belongs to the 19th Century.

               Macmillan’s bicycle was driven by rods attached from pedals to a sprocket on the rear wheel. The first chain-driven bicycle was produced by Tribout and Meyer in 1869. In this year the first bicycle show-in Paris and the first bicycle road race –from Paris to Rouentook place.

              An Englishman, James Starley, of Coventry in Warwickshire, is known as “the father of the cycle industry”. In 1871 he introduced a bicycle with a large driving wheel and a smaller trailing wheel. This was the “ordinary” bicycle, known to everyone as the penny-farthing. In 1874 a chain-driven bicycle with two wheels of equal diameter was designed by H.J. Lawson. This is known as the safety bicycle and became enormously popular from about 1885 when the Rover safety bicycle was built by John K. Starley, James’s nephew.

             The pneumatic tyre - in other words, a tyre filled with air-was invented in 1888 by John Boyd Dunlop, a veterinary surgeon of Belfast, Northern Ireland. By 1893 the design of the bicycle had been developed into the modern diamond frame with roller-chain drive and pneumatic-tyred wheels.

               After extensive us as a pesticide, DDT was found to have many harmful after-effects on human beings and animals. The control of insects was revolutionized by the introduction of DDT after the Second World War. It was employed to combat a wide range of insects which attacked food crops and was also instrumental in bringing the world malaria problem under control. But by the 1960s it was found the DDT affected the metabolism of many birds so much that their eggs became too fragile to survive. As a result many species have nearly become extinct. Several kinds of fish have also been seriously affected. Large numbers of insects which served as food for the both fish and birds have been destroyed.

               The effects of DDT on food for human consumption have been extremely serious. Food becomes poisonous if the amount of DDT in it exceeds a certain limit. However, such pesticides are now heavily restricted b most governments.

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               It is the built-in-skew or twist in a boomerang combined with its spinning motion that makes it return to the thrower. At first people believe that air, pressing on the lower flat surface and passing over the upper rounded face, was responsible for the return flight. But T.L. Mitchell, a Scottish explorer of Australia, gave the true explanation early in the 19th Century.

              The curved throwing stick is used chiefly by the aborigines of Australia for hunting and warfare. (They also use a non-returning kind of boomerang.)

              The boomerang is held at one end above and behind the thrower’s shoulder, with the concave edge of the front and swung forward rapidly with the flat side underneath. Just before it is released, it is given extra power with a strong wrist movement.

              If thrown downward or parallel to the found it sweeps upward to a height f 50 feet or more. When thrown so that one end strikes the found. It ricochets into the air at terrific speed, spinning endwise. It completes a circle 50 yards or more wide and then several smaller ones, up to five, before it drops to the ground near the thrower.

               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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