same heating arrangement, to raise the temperature by ° C, you will find the time taken is again twice that required in the first step. In the third step, in place of water, now heat the same quantity of some oil, say mustard oil, and raise the temperature again by ° C. Now note the time by the same stopwatch. You will find the time taken will be shorter and therefore, the quantity of heat required would be less than that required by the same amount of water for the same rise in temperature.
The above observations show that the quantity of heat required to warm a given substance depends on its mass, m , the change in temperature, ∆ T and the nature of substance. The change in temperature of a substance, when a given quantity of heat is absorbed or rejected by it, is characterised by a quantity called the heat capacity of that substance. We define heat capacity, S of a substance as Q S = ∆ ( . ) where ∆ Q is the amount of heat supplied to the substance to change its temperature from T to T + ∆ T .
You have observed that if equal amount of heat is added to equal masses of different substances, the resulting temperature changes will not be the same. It implies that every substance has a unique value for the amount of heat absorbed or given off to change the temperature of unit mass of it by one unit. This quantity is referred to as the specific heat capacity of the substance. If ∆ Q stands for the amount of heat absorbed or given off by a substance of mass m when it undergoes a temperature change ∆ T , then the specific heat capacity, of that substance is given by S Q s m m ( .
) The specific heat capacity is the property of the substance which determines the change in the temperature of the substance (undergoing no phase change) when a given quantity of heat is absorbed (or given off) by it. It is