Question

S.I. unit of specific heat capacity is
A. Joule per kilogram per kelvin
B. Joule per kilogram per second
C. Degree Celsius per joule per second
D. All

Answer 1

Give the definition of the term specific heat capacity of a substance. From this definition, give the mathematical expression for specific heat capacity and from the physical quantities used in this mathematical expression, give the SI unit of specific heat capacity of a substance.

Complete answer:
The specific heat capacity of a substance is the total heat exchanged by the substance with the surrounding in order to change the temperature of unit mass of the substance by one kelvin.
From this definition of the specific heat capacity of a substance, the mathematical expression becomes
$C = \dfrac{Q}{{m\Delta T}}$
Here, $C$ is the specific heat capacity of a substance, $Q$ is the heat energy exchanged with the surrounding, $m$ is the mass of the substance and $\Delta T$ is the change in temperature of the substance.
From the above mathematical expression, the SI unit of specific heat capacity of a substance is joule per kilogram per kelvin.

So, the correct answer is “Option A”.

Additional Information:
For any substance which is undergoing a phase transition through the physical processes like boiling or melting, the specific heat capacity is infinite because the heat exchanged by the substance is used for its phase transition instead of increasing its temperature.
For a gas being heated in a free state, the specific heat capacity is higher than the gas being heated in a container because in the container, the expansion of the gas is suppressed.

Note:
The unit of temperature used in the given solution is kelvin. But one can also use the unit of change in temperature of the substance as degree Celsius. The amount of heat exchanged is also a form of energy. That’s why the unit of heat is used joule just like the unit of any type of energy.