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CBSE NOTES ⇒ Class 8th ⇒ Science ⇒ Chapter 5. Coal and Petroleum

Chapter 5. Coal and Petroleum

Natural Resources

Chapter 5. Coal and Petroleum  

Natural Resources : Air, water, soil and minerals these all are obtained from nature, they are called natural resources.

Natural Resources are classified into two types: 

(i) Inexhaustible Natural Resources

(ii) Exhaustible Natural Resources

1. Inexhaustible Natural Resources : These resources are present in unlimited quantity in nature and are not likely to be exhausted by human activities.
Examples are: sunlight, air.

2. Exhaustible Natural Resources : The amount of these resources in nature is limited. They can be exhausted by human activities.
Examples of these resources are forests, wildlife, minerals, coal, petroleum, natural gas etc.

Fossil fuels: Some exhaustible natural resources like coal, petroleum and natural gas were formed from the dead remains of living organisms (fossils). So, these are all known as fossil fuels.

Causes to conservate the exhaustible natural resources: 

(i) Exhaustible natural resources like fossil fuels are present in nature in limited quantity.

(ii) These resources can be exhausted in next generations. 

(iii) The process of forming these resources are too longer. 

(iv) Present generation should save these resources for up coming generations. 

Coal: It is as hard as stone and is black in colour.

Uses of coal : 

(i) Coal is one of the fuels used to cook food.

(ii) Earlier, it was used in railway engines to produce steam to run the engine.

(iii) It is also used in thermal power plants to produce electricity.

(iv) Coal is also used as a fuel in various industries.

(v) Coal is processed in industry to get some useful products such as coke, coal
tar and coal gas.

Carbonisation: the slow process of conversion of dead vegetation into coal is called carbonisation.

The process of forming coal: 

About 300 million years ago, earth was having dense forests in low lying wet land areas. Due to earthquakes and vocaline erruptions, these forest got buried under the soil. As more soil deposited over them, they were compressed. The temperature also raised as they sank deeper and deeper. Due to high temperature and lack of oxygen dead plants inside the earth got slowly converted to coal.

Chemical properties: 

Coal burns in abundant air and produces mainly carbon dioxide gas. In less air it produces carbon mono oxide. These are pollutants. 

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