NCERT CLASS 8 SCIENCE CH 3 COAL AND PETROLEUM

 NCERT CLASS 8 SCIENCE CH 3 COAL AND PETROLEUM

1. What are the advantages of using CNG and LPG as fuels?
• CNG and LPG burn cleanly and do not cause pollution.
• They are easy to handle and store.
• They do not leave any ash when they burn.
2. Name the petroleum product used for surfacing of roads.
• The petroleum product used for surfacing roads is called bitumen.
3. Describe how coal is formed from dead vegetation. What is this process called?
• Coal is formed from dead plants and trees that were buried under rocks and soil millions of years ago. Over time, with pressure and heat, the buried plants turned into coal. This process is called carbonization.
4. Fill in the blanks.

(a) Fossil fuels are coal, petroleum, and natural gas.

(b) The process of separation of different constituents from petroleum is called refining.

 (c) The least polluting fuel for vehicles is CNG (Compressed Natural Gas).

5. Tick True/False against the following statements.

(a) False: Fossil fuels cannot be made in the laboratory.

(b) False: CNG is not more polluting than petrol.

(c) True: Coke is nearly pure carbon.

 (d) True: Coal tar is a mixture of various substances.

(e) False: Kerosene is a fossil fuel.

6. Explain why fossil fuels are exhaustible natural resources.
• Fossil fuels are exhaustible natural resources because they take millions of years to form, and we are using them much faster than they can be replenished. Once we use up all the fossil fuels, we cannot make more in a short time.
7. Describe the characteristics and uses of coke.
• Coke is a black and porous substance made from coal. It is mostly made of carbon.
• Coke is used as a fuel because it burns well and produces a lot of heat.
• It is also used in industrial processes, especially in making iron and steel.
8. Explain the process of the formation of petroleum.
• Petroleum is formed from the remains of plants and animals that lived in the sea millions of years ago.
• Over time, these remains were buried under layers of sediment.
• The pressure and heat from the layers of sediment turned the remains into petroleum, which is a thick, dark liquid.