Question

State two differences between ‘heat capacity’ and ‘specific heat capacity’.

Answer 1

Heat capacity is the capability of a substance to absorb heat energy to raise its temperature by one unit while specific heat capacity is the capability of a substance to absorb heat energy to raise its temperature by one unit per unit mass. Both terms are relevant to the subject of heat transfer in liquids and solids.

Complete step by step solution:
-Heat capacity is the heat needed $(Q)$ to change a substance’s temperature by 1K. Hence the heat capacity is usually denoted by $(C)$ has the SI units Joule/Kelvin (J/K). Mathematically, it can be written as:
$Q = C\;\Delta T$
where $\Delta T$ is the change in the temperature of the substance.
Heat capacity depends on the mass of the substance so, for example, for 1kg of substance, it has a heat capacity of 1 kJ/K, then, for 10 kg of substance, the heat capacity will be 10 kJ/K since we will need more heat for raising the temperature of a higher mass of the substance by the same amount.
-Specific heat capacity $(S)$ , as the name suggests, is the specific amount of heat required $(Q)$ to change the temperature of a unit mass of the substance by 1K. Hence for a substance of mass $m$ the heat required to change the temperature by $\Delta T$ is given as:
$Q = mS\Delta T$
Specific heat capacity is independent of the mass of the substance and will be the same for an arbitrary amount of substance mass.

Note:
The difference between specific heat capacity and heat capacity can be remembered because of the term ‘specific’ which corresponds to the specific amount of unit mass for calculating specific heat capacity. Both these quantities have different dimensional formulae too as heat capacity depends on the mass of the substance while specific heat capacity doesn’t depend on it.