NCERT 8th Class (CBSE) Social Science: Minerals and Power Resources

Question: How did minerals influence the history of human civilization?

Answer: Minerals have played and important role in the history of human civilization. Therefore, various stages of human development have been named after minerals, such as:

1. The stone age: marked the time when humans made weapons and implements from stones.
2. Copper Age: Copper was probably the first metal that humans learnt to mine and with its use began the Copper Age.
3. Bronze Age: In the Bronze Age humans developed a stronger and more durable metal by mixing copper and tin.
4. Iron Age: About 3,000 years ago, the Bronze Age was replaced by the Iron Age.
5. Steel Age: Even the Iron Age has been replaced by the Steel Age in modern times.

Question: Why is petroleum called ‘black gold’?

Answer: Minerals oil has great importance in the economy. A variety of products, like petrol, diesel, kerosene, wax, plastics and lubricants are obtained by refining crude mineral oil. Other by-products include raw materials for chemical fertilizers, synthetic fibers and drugs. Thus, it is called ‘black gold’.

Question: Explain the methods of mineral extraction.

Answer: The method used for mineral extraction depends upon the depth at which the minerals occur.

1. When mineral ores occur near the surface, they are simply dug out. This is called Quarrying.
2. When mineral ores are located at a shallow depth, they can be taken out by removing the surface layer. This is called open-pit or open-cast mining.
3. Some mineral deposits occur at great depth. A shaft has to be dug to reach the minerals. Such a mine is called a shaft mine. A shaft mine has many underground chambers. The miners use lifts to reach these chambers.
4. Deep wells are dug to extract oil and natural gas. The process of digging wells and extracting mineral oil is known as drilling.

Question: What are minerals? Discuss different types of minerals on the basis of their composition in detail.

Answer: Minerals are non-living substances which are concentrated in a particular area or rock formation. On the basis of composition, minerals are broadly classified into  metallic and non-metallic.

Metallic Minerals:

1. Metallic minerals are basically found as ores.
2. We get metals such as iron, gold and copper from metallic minerals.
3. Most of the metallic are found in igneous and metamorphic rocks.
4. These minerals are hard and have lustre.
5. The metallic minerals can be further divided into two types – ferrous and non-ferrous.
6. The ferrous minerals contain iron, like iron ore, manganese and chromite.
7. The non-ferrous minerals do not contain iron, but may contain some other metal such as copper, silver, lead and gold.

Non-metallic Minerals:

1. Non-metallic minerals do not have metals in them.
2. They include nitrate, sulfur, potash, salt and coal.
3. Petroleum and coal are used as fuel or sources of power.
4. Therefore, they are also called mineral fuels.
5. Non-metallic minerals are usually found in sedimentary rocks.