My Science School

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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The hydrofoil, a boat supported clear of the water by underwater wings called hydrofoils, was invented by an Italian, Forlanini, in 1898. In 1918 a hydrofoil, powered by an aircraft engine, gained the world’s water speed record. The commercial hydrofoils now used in Europe are based on the work of German engineers who carried out research into the design of high-power, lightweight engines.

       In the early 1950s hydrofoils were developed in the United States, Canada and Russia using high-powered gas turbines. They are used for both military and commercial purposes.

     Since water is 775 times heavier than air, very small hydrofoil wings will support relatively heavy boats. But, since operating in water puts great loads on boats, the hulls are usually built of high-strength steel.

    The object in raising the hull of the hydrofoil from the water is to avoid the resistance caused by friction and drag. This means the power needed to drive the boat at high speeds is cut by half. Another result is that the hydrofoil travels smoothly in quite rough water, and is not slowed down.

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The first flight by a jet-propelled aircraft was made in Germany on August 27, 1939. Its engine was designed by Hans-Joachim von Ohain, who had conceived the idea while a student at Gottingen University in Lower Saxony. Unknown to von Ohain, the British inventor and aviator Frank Whittle had thought of the idea some years earlier. But his engine did not have its first flight until May 14, 1941.

    Briefly, a jet engine takes in air from the atmosphere, compresses it, and uses it in burning fuel. The mixture of hot gases is then expelled through a nozzle in a powerful backward jet which propels the aircraft forwards.

     This forward thrust is the effect of a scientific principle first explained by the English scientist Sir Isaac Newton (1642-1727). He pointed out that with every action there is a reaction which is equal but opposite to it. Thus when a gun is fired, the forward movement of the shell is matched by the backward recoil of the barrel. In a similar way the reaction to the jet exhaust drives the engine forward. The thrust is obtained by the pressure of the jet against the inside of the nozzle and not, as many people suppose, by the exhaust gases “pushing” against the atmosphere.

     The jet engine, whether turbojet, turboprop, ramjet or turbofan, weights less than a piston engine of comparative power and can be much more streamlined.

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The first known lighthouse was the Pharos of Alexandria in Egypt, a 400-foot tower built about 280 B.C.A wood fire was kept burning on the top of the tower, which became one of the Seven Wonders of the world. Before this the light from volcanoes had acted as a guide for sailors. The first light-house in Britain was built by the Romans at Dover in about A.D. 43.

       Lighthouses continued to be built to the plan of the pharos until about the 12th Century. Then oil lamps and candles inside lanterns began to be substituted for fires. Shortly afterwards light houses suffered a decline which lasted until the great expansion of overseas trade and shipping began in the 16th century. This led to a revival and many light houses were built around the coasts of Europe. The first American lighthouse was constructed on little Brewster Island off Boston, Massachusetts in the year 1716.

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The first message in Morse code was tapped out in the United States over a telegraph line from Baltimore to Washington by Samuel Morse in 1844.

        Morse is often credited with the invention of the telegraph on his return to the United States from a trip to Europe in 1832. During this trip he became acquainted with the works of Michael Faraday on electro-magnetism, which forms the basis of the telegraph. This gave Morse the necessary impetus to go ahead with his work.

    In 1837 Morse exhibited his first truly successful telegraph instrument. By 1838 he had developed the Morse code, an alphabet which consists of dots and dashes representing letters and numbers. In the same year he attempted unsuccessfully to persuade Congress to build a telegraph line.

      It was not until 1843 that Congress voted to pay Morse to build the first telegraph line in the United States from Baltimore to Washington. In the following year Morse sent his famous message- “what hath God wrought?” - On this line.

     Later, Morse was caught in a mass of legal claims among his telegraph partners and rival inventors. He was probably the most successful propagator of the telegraph, although there were many pioneers in the same field long before him.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Gamma rays are streams of electromagnetic waves. They are given off from elements such as radium, when they undergo a process known as radioactive decay.

     In 1899 the British physicist Ernest Rutherford began a study of radioactivity. He found three types of radiation which he called alpha, Beta and gamma rays. Alpha rays were stopped by a thin sheet of paper, beta rays could get through several millimeters of aluminum, and gamma rays could pierce quite thick pieces of lead.

      Alpha rays travel at up to 12,000 miles a second, beta rays from 80,000 to 180,000miles a second, and gamma rays at 186,000 miles a second, the speed of light.

     Gamma rays have proved very helpful in medicine and industry. These rays are also given off by radioactive isotopes obtained as by-products in production processes. They can produce radio graphs of forgings and the seams of boilers and other pressure vessels, where freedom from flaws is vital.

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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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If you stood on the shore looking across the sea to the horizon (the line appearing to separate earth from sky), you might be able to see about two and a half miles. But he higher you stood the farther you would be able to see. As the earth is curved, the horizon would appear farther away with every increase in the height above sea level.

       At a height of 20 feet you might see for six miles. From the top of a 300-foot cliff your view could extend for 23 miles, while on the summit of a 3,500-foot mountain, it could lengthen to 80 miles. From an aircraft flying at 16,000 feet you might have an uninterrupted panorama for 165 miles.

If you look straight up into the sky, the distance you can see is immense. The moon is about 239,000 miles away and the stars are millions of miles distant.

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Radar, or radiolocation, as it was called in the early days, is the use of radio waves to find the where-about of aircraft or ships.

    Electromagnetic waves, which include radio and light waves, all travel at the same speed. When small bursts of radio waves, fired into space from a transmitter, strike an object such as an aircraft some of them bounce back and are collected by an aerial. Special equipment calculates the distance of the object from the time taken for the waves to go there and back.

    Direction is obtained by rotating the aerial, and the course being taken by the object is shown as spots of light on the face of a cathode ray tube. So direction, position and movement can be judged accurately.

    Radar was first used to detect enemy aircraft in wartime, and to guide fighter aircraft and bomber pilots. Since then it has proved invaluable in civil aviation by helping the pilot to guide his aircraft in the air and to land it safely in fog or at night.

   At sea it can give the position of land and other ships. Some buoys are fitted with radar, so that they can be located in the dark or in fog. Radar is used also to give warning of turbulent weather.

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Ursa Minor is the name of a group of stars in the Northern Hemisphere. The word used in astronomy for a group of stars is “constellation”.

      The stars and constellations have Latin names. Ursa Minor means The Little Bear. Its brightest star is called Polaris, and is centered over the North Pole. It is of great importance in helping sailors to find their bearing when navigating at night.

    Star maps of the sky will help you locate the constellations.

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It is believed that the Babylonians fist used a pole fixed in the ground to measure the passing of time. They noticed that the position of the shadow changed during the hours of sunlight. They found that the shadow was long at sunrise and that it slowly grew shorter until it reached a point when it started to lengthen again. They learnt to judge the time by looking at the shadow.

        The simple shadow and pole arrangements were the basis of the various shadow clocks or sundials used by the ancient Egyptians. Eventually sundials were provided with the hour figures engraved on a metal plate.

      The Egyptians also used a clepsydra or water clock. This was a basin-shaped, alabaster vessel filled with water that ran out through a hole in the bottom. The time was indicated by the level of water remaining inside.

      Monks were the first to operate clocks by wheels and weights. Clocks of this type, found in monasteries, date back to the 14th Century. The first spring clock is dated about 1500.

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