NCERT / CBSE NOTES | Class 8th (VIII) : Chapter Summary
Mineral and Power Resources
The earth’s crust is made up of hard rocks which are in turn made up of solid substances called minerals. Minerals are formed when natural elements on the earth go through weathering processes such as evaporation of water, extreme heat and pressure.
Metallic minerals contain metal in raw form and are further divided into ferrous minerals and non-ferrous minerals. Ferrous minerals like iron ore, manganese and chromite contain iron. Non-ferrous minerals do not contain iron, but may contain some other metal, such as gold, silver, copper or lead.
Non-metallic minerals do not contain metals like limestone, mica, and gypsum.
Most minerals found in the earth’s crust are in the form of ores and they need to be extracted and purified before being put to various uses.
Minerals can be extracted by: Mining, Drilling and Quarrying. The process of extracting minerals from rocks buried under the earth’s surface is called mining.
The mining process is of two types: Open-cast mining and Shaft mining.
In the open-cast mining process, the minerals are taken out from the shallow depths by removing the surface layer. In the shaft mining process, deep bores (called shafts) are made to reach the mineral deposits that lie deep under the soil layer. In the drilling process, deep wells are bored into the earth’s surface to take out petroleum and natural gas.
Distribution of Minerals
Rocks are mainly of three types -igneous, sedimentary and metamorphic. Different types of rocks contain different types of minerals. Metallic minerals are mostly found in igneous and metamorphic rocks like copper, nickel, platinum, chromites, and iron.
Rocks appear different in colour due to the minerals present in them like the Uluru commonly known as the Ayers Rock in Western Australia is also known to change colour everyday and in every season. Depending on the light falling on it, it changes colours ranging from blue to violet to glowing red.
Non-metallic minerals like limestone and phosphate, and metallic minerals like manganese can be found in sedimentary rocks. Mineral fuels like coal and petroleum are also found in sedimentary rocks.
Asia produces more than half of the world’s tin. China, Malaysia and Indonesia are among the world’s leading producers of tin. Brazil and Bolivia are among the world’s largest producers of tin.
Europe is the leading producer of iron ore in the world. India and China also have large deposits of iron ore. Brazil is the largest producer of high-grade iron ore in the world.
Chile and Peru are the leading producers of copper. South America also has large deposits of gold, silver, zinc, chromium, manganese, bauxite, mica, platinum, asbestos and diamond. Africa is world’s largest producer of diamonds, gold, and platinum. South Africa, Zimbabwe and Zaire produce a large portion of the world’s gold.
Australia is the largest producer of bauxite in the world. It is also the leading producer of gold, diamond, iron ore, tin and nickel.
There is just one country, Switzerland that has no known mineral deposit in it. India has deposits of high grade iron ore. India is the largest producer of mica in the world. Kolar in Karnataka has deposits of gold. These are one of the deepest mines in the world, and hence the mining of this ore is expensive.
India is one of the leading producers and exporters of salt.
Use and Conservation of Minerals
Mineral resources can be found in almost every aspect of our lives. Granite is widely used as building stone is one of the hardest rocks found in nature. It is made up of three minerals - quartz, feldspar and mica. Gypsum is used in plaster cast which is used on broken arms or legs.
The lead in your pencil is made from graphite while crayons and paints are made from talc.
The fireworks are made from yellow-coloured mineral called sulphur, also used for making matches and explosives, sulphuric acid, fertilizers, chemicals and dyestuff.
Copper is a good conductor of heat and electricity obtained from metallic mineral called chalcopyrite or copper pyrite. It so flexible that it can be rolled into flat sheets, wires and other shapes. Hence, copper is used extensively in various electrical appliances. It is also used to make electrical cables and wires, switches, coins, cooking utensils and water pipes. Copper is also used in plumbing, heating, roofing and construction.
Iron is another very important metal that is obtained from minerals such as limonite, hematite and magnetite. These minerals are called iron ores. Iron is mainly used to manufacture steel. Iron and steel are used in almost all industries for manufacturing ships, airplanes, cars, cycles, trucks and vans.
They are widely used in the construction industry to make building support and structures. Iron is also used in the manufacture of computers, and office stationery like staples, nails and paper clips.
The mineral manganese is a key component in the production of iron and steel. Today, the technique devised by the Hittites is called smelting of iron.
Aluminium is another very important metal that is obtained from its ore bauxite. It is used in the manufacture of automobiles and airplanes, and building and electrical materials. It is also used in the bottling and canning industries; kitchen cookware and foil, and personal product like deodorants and cosmetics.
Gold and silver are rare metals that are popularly used to make jewellery. They are also used to make medallions and coins, and in dentistry and medicine.
Certain minerals, called gemstones, are also used to make jewellery. They are hard and come in many beautiful colours. Some gemstones, like diamonds, sapphires, emeralds and rubies, are rare and very expensive and are known as precious stones.
Some gemstones, like turquoise, garnet, amethyst, aquamarine, topaz, moonstone, peridot and opal, are not as rare and so are known as semi-precious stones.
Gemstones are first cut and polished, then set into precious metals like gold, silver and platinum to make artistic jewellery.
Diamond is the hardest mineral found on the earth and so is used for making cutting tools that are used for cutting other gemstones.
Minerals are also very essential for all living beings.
Iron is present in every living cell. It is very essential for the production of haemoglobin, which is the primary component of red blood cells. Other minerals like zinc, manganese, copper and fluoride are also required in very small amounts in our diet.
Minerals are non-renewable resources. It is very important to control their use and conserve minerals for the future.
There are three ways of conserving minerals for future use – reduce, recycle, reuse.
You can reduce the amount of waste you create by choosing what rubbish you throw away. Recycling means to return a waste product to a place where it is remade into either the same product or something different. The reuse of metals will also help in reducing the rate of consumption, and help in the conservation of minerals.
Energy is required to perform various activities in every field. Heat and electricity are two different forms of energy. The most common sources of generating heat and electricity are firewood, coal, petroleum and natural gas. These sources are called conventional sources of energy.
Firewood is primarily used for cooking and heating. However, it is not a very convenient and eco-friendly source of energy. Collecting firewood and cooking with it is time consuming and also burning firewood releases carbon monoxide in the air. This results in air pollution and higher levels of greenhouse gases. Firewood is also the main cause of deforestation.
Fossils are remains of plants and animals that were buried under the earth for millions of years. Coal, petroleum and natural gas are fossil fuels as they are formed from fossils.
Coal however, has its own set of disadvantages. Apart from being bulky to transport, it is also a source of pollution. The major coal producing countries in the world are China, the USA, Germany, Russia, South Africa, and France. In India, the major coal producing areas are Raniganj, Jharia, Dhanbad and Bokaro in Jharkhand.
About 80% of coal is mined from the Damodar Valley.
Petroleum is another important conventional source of energy. The word petroleum means rock oil and is found between layers of rocks in the form of a thick black liquid.
In its raw form petroleum is called crude oil which is drilled from oil fields located in off-shore and coastal areas. The major petroleum producing countries in the world are Iran, Iraq, Saudi Arabia and Qatar.
A major advantage of petroleum is that it can be easily transported in tankers. Natural gas is another fossil fuel that is traditionally used as a source of energy. It is found with petroleum deposits and is released when the crude oil is brought to the surface.
Electricity is also generated from the energy of flowing water. The energy derived from flowing water is called hydropower. The electricity generated from hydro power is called hydroelectricity. Norway was the first country in the world to develop hydroelectricity. The leading producers of hydro power in the world are Paraguay, Norway, Brazil, and China.
The fossil fuels are limited in stock and hence it is important to conserve these fossil fuels.
Non-conventional Sources of Energy
Firewood and Fossil fuels like coal, petroleum and natural gas called fossil fuels, are non-renewable and limited in stock. Energy from the sun, wind and tides, nuclear energy, energy from the earth and from decayed organic matter are called non-conventional sources of energy. These are renewable, unlimited and eco-friendly.
The primary source of all energy on the earth is the sun and its heat or light is called solar energy. Solar energy is an inexhaustible and non-polluting form of energy.
A device called a solar panel is used to convert solar energy into heat and electrical energy. A solar panel is made up of a number of solar cells that absorb solar energy and convert it into electricity. Solar energy can be effectively used in tropical countries that receive abundant sunlight.
Wind is another natural source of energy that is inexhaustible and is a non-polluting, low-cost, safe and clean source of energy. The energy generated from winds is called wind energy.
In olden times, wind mills were used for grinding grain and lifting water. Today, wind mills are used to produce electricity. The major disadvantages of wind energy are that it contributes to noise pollution and can be harmful to birds.
The energy stored in the nuclei of radioactive elements like uranium and thorium is known as nuclear energy. Nuclear energy is produced when the nucleus is split apart and this phenomenon is known as nuclear fission. During nuclear fission, tremendous amount of heat and light energy is released.
The earth also has a considerable amount of heat energy stored inside it. This energy is called geothermal energy, where geo means earth and thermal means heat. This energy is clean and eco-friendly. Geothermal energy can be seen dissipated on the earth’s surface in the form of hot springs, natural geysers and volcanoes.
The gravitational pull of the moon and the sun and the rotation of the earth result in causing tides. Energy generated from tides is called tidal energy. It is a non-polluting and inexhaustible source of energy.
Another renewable source of energy is biogas which is produced from bio mass. Biomass includes wood from trees, matter from dead plants and animals, waste from other plants, animal dung and kitchen waste.
It can be used to generate electricity, light, heat, motion and fuel. Biogas is a low-cost source of energy, easy to operate, and uses bio-waste.