1. Name the type of nuclear reaction taking place in the atmosphere of Sun.
2. Define ignition temperature.
3. Why water should not be used to put out fire caused by burning of petrol.

1. Nuclear fusion is the type of nuclear reaction taking place in the atmosphere of the Sun.
2. The minimum temperature to which a substance is heated before it starts burning is known as ignition temperature.
3. Petrol is lighter than water, so it floats on top of the water and keeps continuously burning. Hence, water should not be used for extinguishing fire due to burning of petrol.