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Published on Aug 27, 2012
IGNITION TEMPERATURE Ignition temperature of a substance is the minimum temperature required for the substance to catch fire. The substances which have a very low ignition temperature and catch fire at a very low temperature are called inflammable substances. Petrol and LPG are the examples of inflammable substances. The following activity shows that for a substance to catch fire, it must be heated to its ignition temperature. Prepare two paper cups in the shape of a cone and fill one of the cups with water. Heat these two cups separately on the steady flame of a candle. The empty paper cup catches fire very quickly but the paper cup filled with water doesn't catch fire easily. This can be explained as follows. The empty paper cup has nothing but air inside it and burns as soon as its ignition temperature is reached. The paper cup with water doesn't catch fire because the heat supplied to it is conducted to the water inside it. Hence the presence of water increases the ignition temperature of the paper and the cup doesn't burn.