My Science School

                Oil is thought to have formed from the remains of organisms that died millions of years ago. Billions of tiny organisms lived in shallow water or in the surface layers of the oceans. As they died their remains settled to the bottom and were eventually buried. The remains were compressed under the weight of rock. They underwent chemical changes due to the high pressure and eventually formed oil and gas, which remained trapped under the rock layers.

               Geologists locate deposits of oil, and holes are drilled so the oil can be extracted. Usually, water is pumped into an oil well under pressure, forcing the lighter oil up to the surface.

               Coal is formed from the compressed remains of plants that lived in bogs 250-350 miff on years ago. This was during the Carboniferous Period, when primitive animals first appeared on the land. Coal formed from the remains of tree ferns and other primitive trees, which were covered with mud and sand and buried as new rock was laid down. Very gradually, over millions of years, this material turned into coal.

               A similar process is taking place today in peat bogs, where the rotting remains of heather form peat. When dried, peat burns in a similar way to coal. In some parts of the world soft shale, which is called brown coal, is mined. The hardest and most pure form of coal is anthracite, which contains very few impurities.

Picture credit: google

               Gold is unusual because it is found in its metallic form, rather than as a chemical compound. Metallic gold, which is easy to identify and shape, has been mined for thousands of years. Most gold is found in what are called alluvial deposits. They consist of river mud containing tiny particles of gold washed out of rock over thousands of years. Water currents are used to wash away the mud and gravel, leaving the heavy gold particles. Gold is mined in many parts of the world, but most modern gold supplies come from countries such as South Africa and Russia.

               Gold does not tarnish, and this makes it very valuable.lt is used mainly for the manufacture of jewellery and for coating electrical contacts. It is also a very good conductor of electricity.

               The earliest form of mining involved following seams of metal in tunnels driven into the rock. This method is still used today, usually in deep mines where other techniques would be impracticable. Tunnels are dug with explosives and with automatic machines. Some of these mines go thousands of metres into the rock, becoming very hot and dangerous.

               Placer mining uses huge floating dredgers to extract metals such as tin and copper from submerged mud. It extracts large amounts of metal inexpensively, but causes enormous environmental damage. Strip mining is used to obtain coal and minerals that lie close to the surface. Open pit mining involves blasting into the rock to produce a huge quarry from which material is removed, layer by layer.

Picture credit: google

 

               Mining has taken place since the Stone Age, when flints were mined for making stone tools. By 3500BC, people were mining for copper, which they soon combined with tin to harden it and make tools and weapons. Today we mine minerals, diamonds, metals, coal and rock for building material, using a variety of techniques.

Picture credit: google

 

               Explosives are substances that release a very large amount of energy in a short time when they burn. They all contain a fuel plus an oxidizer, which is a substance containing sufficient oxygen to burn the fuel. Explosives do not need air to explode, because they contain their own oxygen, and so they can burn in confined spaces or even underwater. Some explosives, such as those in a cartridge detonator, explode violently when hit or heated. Others only cause a violent explosion when confined in a gun barrel or a hole drilled in rock for blasting.

               Gunpowder, the first ever explosive, was invented in China over 1,000 years ago. Large amounts of modern explosives are commonly used in quarrying and mining, as well as for munitions.

Picture credit: google

 

               Plastics are synthetic materials that consist of long chains of molecules called polymers. When the chains are positioned in long rows the plastic is rigid. When the polymer molecules are tangled together, the plastic is soft and flexible. All plastics can be moulded under pressure into complicated shapes. Thermoplastics melt when they are heated, and this means that they can be remelted at any time. There are other forms of plastic known as thermosetting plastics, which cannot be remelted.

               The majority of plastics are made from synthetic resins, which are usually derived from oil. Other types come from sources such as coal or wood. As they do not conduct electricity, most plastics are excellent insulators, so are widely used in electrical wiring. The main disadvantage of plastics is that they are very slow to break down, causing serious environmental problems when discarded.

Picture credit: google

               Natural rubber comes from a kind of tree that originally grew in South America. Its liquid sap, called latex, is drained from the tree by making cuts in the bark.  The latex is collected and processed into rubber. Natural rubber is very soft and is used for making the soles of shoes and sandals.

               In 1839 Charles Goodyear, an American inventor, found that heating rubber together with sulphur made it much harder. This process, known as vulcanization, made it possible to use rubber for vehicle tyres. Rubber is now used for electrical insulation, motor tyres, cushions, golf balls and many other applications.

               Since World War II most of the rubber we use has been produced synthetically. Rubber’s properties are based on the way its molecules link up into long chains, making giant molecules called polymers.

Picture credit: google

            Steel is made from iron, which is usually mined in the form of iron ore. The ore needs to be smelted in order to extract the iron. Smelting is done in a blast furnace, where coke and limestone are added to the iron ore. This mixture is heated to a very high temperature and air is blown through it. The molten iron is drawn off.

            To make steel, iron is mixed with carbon and other metals to give it extra harness. There is about 1.6 percent carbon in most steel. Other forms of steel contain elements such as chromium and nickel to prevent rusting. Ordinary carbon steel rusts as easily as iron, and must be protected with paint or other coatings.

Picture credit: google

            The nucleus of an element normally has a fixed number of protons and neutrons. Some elements exist in different forms, however, with varying numbers of neutrons in their nuclei. A radioisotope is an element that releases radioactivity. Its nucleus is unstable. It can only become stable by releasing radiation and energy in the form of heat and particles. These are split off from the nucleus. Radioisotopes such as iodine and cobalt are widely used in medicine. They are particularly helpful in the study of organ function.

            Radioisotopes are known to have a steady rate of decay. This means that we can use them to accurately date fossilized remains. Carbon-14 is used in this way.

Picture credit: google

            Particles continuously escape from the nucleus of radioactive elements, in a process called radioactive decay. Half-life is the time taken for half of a substance’s atoms to decay into different element. Uranium-235 has a half-life of nearly 250,000 years, while polonium-214 has a half-life of a tiny fraction of one second.

Picture credit: google

            Nuclear fusion is a means of producing energy that involves fusing together the nuclei of light, non-radioactive substances. This process takes place in an uncontrolled way in hydrogen bombs. Machines called particle accelerators fire tiny particles at a target and produce fusion. It has not been possible to use nuclear fusion to generate power for electrical supplies.

Picture credit: google

            A nuclear reactor is used to control nuclear fission. In most reactors, uranium is encased in metal tubes that are inserted into the reactor. The tubes are surrounded by a moderator, such as graphite, that slows sown the reaction.

            In another form of reactor the fuel rods are surrounded by low-grade uranium, and the neutrons escaping from the reactor strike this material. The radiation converts the low-grade uranium into plutonium, which can be used as a nuclear fuel. This type of reactor, called a fast-breeder reactor, produces more plutonium that it can use as fuel. Although this sounds very useful, plutonium is much more dangerous to handle than uranium, and there are serious safety problems in its use.

Picture credit: google

          Atom bombs are a form of uncontrolled nuclear fission. When a large enough mass of uranium is put together, a fission reaction starts. The flood of neutrons emitted becomes so enormous that a vast amount of energy is released in a very short time, producing an atomic blast.

            Hydrogen bombs have an atomic bomb at their heart, but this core is surrounded by a layer of light material. Using the power released from the fission of the uranium or plutonium core, this layer of material causes a fusion reaction like the one in the core of the Sun. this nuclear fusion releases more heat energy than a fission explosion, as well as huge amounts of radioactivity.

Picture credit: google

 

               Once nuclear fission takes place inside a nuclear reactor, the chain reaction has to be controlled, or moderated. The reactor’s core of uranium is surrounded with a substance that slows down and absorbs the escaping neutrons. The moderating material becomes heated. In a nuclear power station, steam generated by this heat is used to drive the turbines to produce electricity.

Picture credit: google