Give reason for the following :
Paper by itself catches fire easily where as a piece of paper wrapped around an aluminium pipe does not.
When paper is heated alone, its ignition temperature is reached quickly due to which it catches fire easily. When the paper wrapped around an aluminium pipe is heated, then the heat supplied to paper is transferred to aluminium pipe by conduction. Due to the continuous transfer of heat from paper to aluminium pipe, the paper does not got heated to its ignition temperature quickly and hence does not catch fire easily.
When a lot of dry powder of a substance X is released over a fire, the fire gets extinguished.
(a) Name the substance X.
(b) How does the substance extinguish the fire ?
(c) Name another substance which behaves like X.
An electric spark is struck between two electrodes placed near each other in a closed tank full of petrol. Will the petrol catch fire ? Explain your answer.
How does carbon dioxide help in putting off fire ?
What type of combustion is represented by :
(a) burning of white phosphorus in air at room temperature ?
(b) burning of LPG in a gas stove ?
(c) ignition of a cracker ?
(d) burning of coal dust in a coal mine ?
