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sir plz give more qestion on on combustion and flame

1. List conditions under which combustion can take place.

Ans. Conditions necessary for combustion are:

    Presence of combustible substance.
    Attainment of ignition temperature.
    Proper supply of air to provide oxygen.

2.Explain how the use of CNG in automobiles has reduced pollution in our cities.

Ans. The use of CNG in place of petrol and diesel reduce pollutions in following ways.

    It produces less carbon monoxide gas.
    It produces less carbon dioxide gas.
    It produces less amount of sulphurdioxide and nitrogendioxide which cause acid rain.
    No residue remain after combustion.

3.Give reasons.
Water is not used to control fires involving electrical equipment
Ans, Water is a good conductor of electricity. It conducts electricity and may result electric shock.
    
LPG is a better domestic fuel than wood.
Ans, LPG has more caloric value and produces no pollution. So it is better domestic fuel than wood.

Paper by itself catches fire easily whereas a piece of paper wrapped result electric aluminium pipe does not.
Ans, The ignition temperature of paper is less, so it catches fire easily. It does not catch fire when wrapped around aluminium pipe because aluminium absorbs the heat so paper does not attain its ignition temperature.


4.It is difficult to burn a heap of green leaves catch fire easily. Explain.
Ans. The green leaves contain some water due to which the ignition temperature of leaves increases and they do not catch fire easily while dry leaves have no water so they catch fire easily.

5.What are characteristics of a good fuel?

Ans: Characteristics of a good fuel:

i. It should be readily available.                  
ii. It should be cheap.     
iii.It burns easily in the air at moderate rate.       
v. It produces a large amount of heat.             
vi.It does not leave behind any undesirable substances.


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