1. In summer, white phosphorus begins to burn on its own. 2. A matchstick can be lit by striking it on a rough surface of a floor. 3. Dry wood is ideal an ideal fuel for camp fire. 4. Biogas is a renewable source of energy. 5. In a burning candle, the wax below the flame melts but does not catch fire. 6. Combustion of petrol produces heat. 7. We should not use mobile phones in petrol pumps. Give scientific reasons for each of the following.

1. In summer, white phosphorus begins to burn on its own because of the heat. 2. A matchstick can be lit by striking it on a rough surface of a floor because of the friction. 3. Dry wood is an ideal fuel for camp fire because it can catch fire very easily. 4. Biogas is a renewable source of energy because we can regenerate it by adding cowdung. 5. In a burning candle, the wax melts but does not catch fire because though it has oxygen and fuel, but down below, sufficient heat is not present for the candle to burn. 6. Combustion of petrol produces heat because when we turn on any transport and ride in it, the petrol is burnt and it gets converted into a smoke because of a reaction. 7. We should not use mobile phones in petrol pump because when we talk on phone, the static electricity gets built-up. So our clothes can catch fire as petrol is highly flammable.