Question

Explain the following.

a. Diamond, graphite and fullerenes are crystalline forms of carbon.

b. Methane is called marsh gas.

c. Petrol, diesel, coal are fossil fuels.

d. Uses of various allotropes of carbon.

e. Use of CO₂ in fire extinguisher.

f. Practical uses of CO₂

Answer 1

a. Diamond, graphite and fullerene are crystalline forms of carbon. They are allotropes of carbon and this property of carbon is termed as allotropy. These crystalline forms of carbon have a regular and definite geometrical shape, sharp edges and plane surfaces.

b. Methane is called marsh gas because it is found at the surface of marshy places (a type of wetland, an area of land where water covers ground for long periods of time which are usually treeless and is dominated by grasses and herbaceous plants).

​c. Petrol, diesel, coal are fossil fuels because they are fuels obtained from fossils such as dead sea organisms, dead plants and animals, etc is known as fossil fuel. They are formed from the dead remains of living organisms, both aquatic and terrestrial, which have been buried for millions of years under the ground.

d.

Allotropes of carbon	Uses of allotropes
1. Diamond	used in glass cutting and rock drilling machines used in ornaments diamond knives are used in the eye surgery diamond dust is used for polishing other diamonds used to make windows giving protection from radiation in space and in artificial satellites
2. Graphite	used for making lubricants used for making carbon electrodes used in pencils for writing used in paints and polish used in arc lamps which give a very bright light
3. Fullerene	used as insulators used as a catalyst in water purification
4. Coke	used as fuel in factories and homes used to obtain coke, coal gas and coal tar used in thermal power plants for generation of electricity
5. Coal	used as fuel in factories and homes used to obtain coke, coal gas and coal tar used in thermal power plants for generation of electricity

e. CO₂ is used in fire extinguishers for various reasons but the main reason is that the carbon dioxide gas displaces the oxygen that's necessary to maintain combustion. It means that it cuts of the supply of oxygen which is required for combustion and also it has a cooling effect when it is released under high pressure. Other uses of carbon dioxide in fire extinguishers is

• it does not conduct electricity thus making it an ideal fire suppressant for use in electrical instruments like computers etc.
• it does not create any toxic or other by-products when used to suppress a fire.

​f. The practical uses of CO₂ are:

• it is used for getting special effects of a mist in dramas and movies
• it is used to make aerated drinks
• solid carbon dioxide is used in cold storage and also to keep milk and milk products and frozen substances cool during transport
• liquid CO₂ is used as solvent in modern eco-friendly dry cleaning
• CO₂ obtained by chemical reaction or kept under pressure is used in fire extinguishers
• plants use CO₂ in air for photosynthesis