Important Terms

Mineral: Mineral is a natural chemical compound, uniform in compositions and structure and is a constituent of rocks and ores.

Mining: Mining is the process of extracting minerals from rocks buried under the earth surface. There are two types of mining – Open cast mining and Shaft mining.

Open cast mining: The process of taking out minerals from rocks buried under the surface of the earth at shallow depths by removing the over-burden (surface layer) is known as Open cast mining. Open cast mines of coal can be seen in Raniganj (West Bengal) and Singrauli (MP).

Shaft mining: The process of taking out minerals from great depths through deep bores called shafts is known as Shaft mining. In Jharia – Dhanbad belt (Jharkhand) we find coal mining is being done through this process.

Quarrying: Process of digging out of minerals from shallow depths under the surface is known as Quarrying. For examples, Limestone, Quartzite etc are taken out through this process.

Drilling: Deep bores made for taking out petroleum and natural gas are termed as drilling. In other words it is the process by which we extract oil and natural gas from oil wells which occur in sedimentary rocks.

NCERT Textbook Exercise (Important Questions only)

Q.1: Answer the following questions

(i) Name any three common minerals used by you every day.

(ii) What is an ore? Where are the ores of metallic minerals generally located?

(iii) Name two regions rich in natural gas resources.

(iv) Which sources of energy would you suggest for

a. Rural areas

b. Coastal areas

c. Arid areas

(v) Give five ways in which you can save energy at home.


(i) Petroleum, Iron, Aluminium

(ii) Rocks from which minerals are mined are known as ores. For any material to be called ore of any mineral, it must contain minimum adequate quantity of that mineral so that it can be extracted profitably.

(iii) World: Russia, Norway, UK, Netherlands. India: Jaisalmer, Krishna – Godavari delta, Tripura, Off-shore areas of Mumbai

(iv) These are –

1) Rural areas: In rural areas primary occupation of the people are agriculture and rearing of the cattle. So the organic waste and human waste are available here in plenty which can be converted into Biogas. Other sources of energy are firewood, coal, and solar energy etc.

2) Coastal areas: The successive rise and fall of the sea water or tides near coastal areas can be a good source of generating energy called Tidal energy. Some other sources of energy in coastal areas are wind energy. Natural gas and petroleum are also available in the off-shore areas. So, these can also be the sources of energy in some coastal areas.

3) Arid regions: Very high temperature due to sun’s heat is typical of arid regions. The energy trapped from the sun’s rays known as solar energy can be utilized to produce electricity.

(v) The five ways are –

1) We should put light and fans off when not in use.

2) We should not waste water unnecessarily.

3) Food should be cooked in pressure cooker.

4) We should use fuel carefully so that it does not get exhausted quickly e.g. put off gas oven in kitchen when not in use.

5) Save petrol by following driving rules properly.

Q.3: Give reasons:

(i) Environmental aspects must be carefully looked into before building huge dams.

(ii) Most industries are concentrated around coal mines.

(iii) Petroleum is referred to as “Black Gold”.

(iv) Quarrying can become a major environmental concern.


(i) Environmental aspects must be carefully looked into before building huge dams because of the following reasons –

1. Dams create imbalance in the earth’s equilibrium.

2. Deforestation leads to environmental pollution.

3. People become displaced.

4. Cities / villages / towns may require shifting causing lot of hardships for the people.

5. Flood threats loom large.

6. Earthquake threats

7. Silting of lakes is a problem.

(ii) Coal is used as a source of energy and power and also as a raw material in most of the industries. Hence most industries are concentrated around coal mines of the purpose saving cost of transportation of coal (cost effectiveness).

(iii) Petroleum is referred to as “black gold” because it is black in colour in the crude form and its derivatives are extremely valuable as petroleum itself. Today it is almost inevitable in our day-to-day life. A variety of products like – kerosene, diesel, petrol, wax, plastics, lubricants etc. are produced from these mineral resources.

(iv) Quarrying can become a major environmental concern because of the following reasons:

1. It may destroy the humus of soil which is much required for the growth of plants and crops.

2. It produces a lot of noise pollution due to use of explosives at times in order to break the huge chunks of rocks.

3. In the process of quarrying lot of dust is generated which causes air pollution and also occupational hazards.

4. Blasting done in the process of quarrying generate vibration which damage in the nearby buildings, dams or any other similar structure.

Q.4: Distinguish between the following:

(i) Conventional and Non-conventional sources of energy

(ii) Biogas and Natural gas

(iii) Ferrous and Non-ferrous minerals

(iv) Metallic and Non-metallic minerals


(i) Distinction between conventional and non-conventional sources of energy can be done as follows:

Conventional Source of Energy Non-conventional Source of Energy

1. Conventional sources of energy are those sources which have been in use from time-immortal.

2. They are exhaustible except water (hydro – energy).

3. They cause pollution when used as they emit smoke and ash.

4. Their generation and use involve huge expenditure.

5. Very expensive to maintain, store and transmit as they are carried over long distances through transmission grids.

6. Examples are – coal, petroleum, natural gas, water, fire-wood. 1. Non-conventional sources of energy have generally been identified in the recent past.

2. They are inexhaustible.

3. Generally these are pollution free.

4. Low expenditure required.

5. Less expensive due to local use and easy maintenance.

6. Examples are – geothermal energy, solar energy, wind energy, tidal energy, biogas energy, nuclear energy etc.

(ii) Distinction between biogas and natural gas can be done as follows:

Biogas Natural gas

1. It is a non-conventional source of energy.

2. Organic wastes such as farm wastes, animal dung, kitchen and some human wastes are converted into a gaseous fuel which is called biogas.

3. It is more common in rural areas.

4. It is an excellent fuel fore cooking and lighting.

5. Biogas is a mixture of methane and carbon-dioxide. (May cause green house-effect).

6. Involves low cost and easy to operate. 1. It is a conventional source of energy.

2. Natural gas is found associated with petroleum deposits.

3. An exhaustible natural resource, found in India in Jaisalmer, Krishna – Godavari basin, Off-shore areas of Mumbai, Tripura, Sunderban (WB) and Assam.

4. Used domestic as well as industrial fuel. Also as a raw material for fertilizer industry, power generation plants etc.

5. Cleaner than other fossil fuels.

(iii) Distinction between ferrous and non-ferrous minerals can be made as follows:

Ferrous minerals Non-ferrous minerals

1. The minerals having iron contents are called as ferrous minerals. Examples – iron ore, manganese ore, chromium etc.

2. India abounds in ferrous minerals. 1. The minerals that do not contain iron are called as non-ferrous minerals. Examples – gold, lead, zinc, copper silver etc.

2. India is deficient in non-ferrous minerals.

(iv) Distinction between metallic and non-metallic minerals can be made as follows:

Metallic minerals Non-metallic minerals

1. The metallic minerals contain metals in raw form. Examples – iron ore (hematite), aluminium ore (bauxite) etc.

2. They are often hard and shiny.

3. Metals are extracted from these by smelting.

4. Generally found in igneous and metamorphic rocks. 1. The non-metallic minerals do not contain metals. Examples – limestone, gypsum, coal, petroleum etc.

2. They lack metallic luster.

3. These minerals can not be smelted.

4. Can be found in all types of rocks i.e., igneous, metamorphic and sedimentary rocks.

HTTP://CBSEKEY.COM(Additional Important Questions)

Long Questions with their Answers

Q.1: Give an account of Biogas.

Fig: Biogas Generation

Ans: Organic wastes like dead plant and animal materials, animal dung kitchen wastes are converted into a gaseous fuel called biogas. The organic waste is decomposed by bacteria in biogas digesters to emit biogas. It is a mixture of carbon-dioxide and methane. Biogas is an excellent fuel for cooking and lighting. Moreover, biogas plants produce a huge amount of manure each year.

Fig: Obtaining Geothermal Energy

Q.2: How is geothermal energy used?

Ans: Heat energy obtained from earth is called geothermal energy. The temperature in the interior of earth increases with the increase of depth. This heat energy comes to the surface of the earth in the form of hot springs which can be used for various purposes like – to generate power, for cooking and also bathing. It is believed that bathing in hot springs heal many diseases. In India geothermal power are located in Manikaran (Himachal Pradesh) and Puga valley (Ladakh). Geothermal power is also found in other parts of the world e.g. USA, New Zealand, Iceland, Central America and Philippines.