Category Chemistry

What is hard water?

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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When does an atom split?

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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Why are some metals chromium plated?

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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Why do exhaust fumes contain lead?

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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Our Planet Earth

 

What are metals?

Metals are one of the major groups of elements. Most of them are shiny and hard. Mercury is the only metal that is a liquid at normal temperatures. Most metals can be bent and stretched, and they can be mixed to make alloys.

Metals are usually found with other elements in the form of compounds. Bauxite is an ore, or mixture of substances, that contains aluminium, the commonest metal. It makes up about eight percent of the Earth’s crust. Osmium is the heaviest metal, and is twice as heavy as lead. Lithium is the lightest metal. It is half the weight of the sane volume of water, so it floats in water.

 

 

 

 

 

How much of the Earth is covered by water?

More than two-thirds of the Earth’s surface is covered by seas and oceans. About 72 percent of the Earth’s surface is water. This water is either in the oceans, locked away as ice at the poles, or held as water vapour in the atmosphere. All of the Earth’s water is known as the hydrosphere. 

 

 

 

 

 

 

 

 

Why is the Earth round?

Gravity pulled the Earth and the other planets into a sphere when they were being formed. The Earth is not truly round, but is slightly flattened making it bulge out at the Equator. This effect is due to the speed with which the Earth spins, causing the Equator to try to fly out from the axis of the spinning Earth. It is rather like a heavy object whirling round on the end of a piece of string. The shape of some of the other planets is distorted in the same way.

RICHES OF THE EARTH

All the metals we use are taken from the Earth. Most of them are found in rocks, combined with other substances, while some, like gold and copper are found as pure metal. Many of the ‘fossil fuels’ we use, like coal, gas and oil, are also taken from the Earth. Coal is usually dug out of the ground while gas and oil are extracted by drilling deep holes in the Earth.

Rocks in the Earth’s crust can often be used for specialized jobs. For example, one rock called ‘mica’ is found in thin transparent sheets. It can be used to make windows for high-temperatures ovens, where glass would melt.

 

 

How coal was formed

Coal has formed over millions of years from the remains of ancient forests growing on swamps.

As forest trees and plants died, they fell into the swamps forming layers of dead vegetation. Later, sedimentary rocks formed on top of these layers.

The pressure caused by the rocks made the layers of vegetation denser and harder and formed them into a solid rock – coal.

 

 

 

 

 

Coal is a fossil fuel often mined from underground.