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Uranium
The importance of uranium today lies in its value as a producer of nuclear power. Uranium was first discovered by the German chemist, Martin Klaproth in 1789. But for a century and a half afterwards few uses could be found for the new metallic element.
Some suggested making filaments for lamps out of it. Uranium has actually been used successfully in large lamps for photography. Also, it was of some value as a dye for wood and leather.
In 1938, two scientists, Hahn and Strassmann, discovered that uranium could yield nuclear energy. One pound of uranium would give as much energy as three million pounds of coal. The first nuclear chain reaction was conducted by Enrico Fermi in 1942. This made possible the exploding of the first atomic bomb in 1945.
Apart from its destructive applications, the use of uranium in nuclear power stations has proved a valuable substitute for the world’s dwindling supply of oil and coal. Also, isotopes extracted from uranium have proved immensely useful have proved immensely useful in medicine by helping to diagnose and treat illnesses.
Liquids that 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 reaction 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-glycerine.
Liquid Air
Liquid air is a mixture of oxygen and nitrogen, which have been compressed until they form a liquid. When the pressure on the liquid is released, it turns back into these two gases. The liquid is kept under great pressure in strong cylinders.
Liquid air has great many uses, because it enables large amounts of these two gases to be stored in small spaces. The aqualung used by skin drivers consists of small cylinders joined to a mouthpiece. Pilots, fireman and astronauts also use liquid air.
Once liquid air has been made, th3e liquid air has been made; the liquid oxygen can be separated from it for use in hospitals. People with lung trouble are helped by being given an increased amount of oxygen to breathe. Other gases, liquefied in the same way, aroused as anesthetics to put people to sleep during operations.
Liquid oxygen is widely used in industry because a flame fed with additional oxygen is much hotter than an ordinary flame. The oxy-acetylene torch consists of two cylinders, one of liquid oxygen and the other of acetylene. The two gases are mixed together and fed through tubes to a special blowpipe. When
They are lit; they can produce a flame with a temperature of about 3,000 centigrade (5,432 Fahrenheit) or twice the melting point of iron. This torch is used to cut and to weld metals.
Splitting the Atom
An atom splits when a neutron strikes it. 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 power full microscope. They are the building bricks of which each element is composed. The Greek word "atom" means, "cannot be cut". But we know now 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 the nucleus could be divided into several parts. Albert Einstein (1879-1955) calculated in 1905 that heat ought to have weight and that, if we could destroy a pie of matter and turn all its weight into heat, we should obtain vast amounts of heats by using up only a small amount of matter.
Between 1934 and 1938 the Italian Enrico Fermi and the4 German Otto Hahn discovered that atoms of uranium (atomic weight 92) spilt when struck by a neutron. In 1939 Fr3e4deric 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.
Satellite
An artificial satellite remains in its regular course around th3e earth even after its motors have been turned off. This is not because the satellite has been lifted beyond the reach of gravity but because the satellit3e has been lifted beyond the reach of gravity but because its centrifugal force just balances the gravitational pull of the earth.
Launching a satellite calls for a propellant, such as a rocket, which can move it high enough and fast enough to make it orbit the earth at a constant height indefinitely. There is no air in space to slow it down
Since the pull of gravity grows less as the distance from the earth's surface increases; -its orbital velocity-also grows less.
At a height of 200miles the orbital speed required is 17,200m.p.h. At about 22,000miles, the required speed would cause the satellite to take 24 hours to complete an orbit. It would thus cause rotate with the earth and maintain a fixed position.