Question

The specific heat capacity of water in SI unit is:
$\begin{align}
  & A.4.2\dfrac{J}{gK} \\
 & B.42\dfrac{J}{gK} \\
 & C.420\dfrac{J}{kgK} \\
 & D.4200\dfrac{J}{kgK} \\
\end{align}$

Answer 1

Hint: Specific heat capacity of a substance is the amount of energy absorbed or released by a body per 1kg mass for 1K increase or decrease in temperature. Hence, the unit of specific heat capacity is a complex unit of the form energy per mass per temperature. The SI unit can be found out by plugging in the SI units of these physical quantities in the proper manner.

Complete step by step answer:
The total amount of thermal energy absorbed or released by a body when its temperature increases or decreases respectively, depends upon the specific heat capacity of the body.
Therefore the units of specific heat capacity should be $\dfrac{E}{m\times T}$
Where E is energy, m is mass, and T is temperature.
So the specific heat capacity of water is 4200$\dfrac{J}{kgK}$.

So, the correct answer is “Option D”.

Note: Students may get confused with specific latent heat and specific heat capacity. However, they are different. Specific latent heat is the thermal energy required by a body per unit mass for a phase change. During this time, the temperature of the body does not change. This can be remembered by understanding the meaning of the word latent which means hidden. Since there is no temperature change involved in specific latent heat, it seems like all the heat has been hidden inside the body. Therefore, there is no relation of temperature with the specific latent heat but specific heat capacity involves a unit temperature change. On getting confused students might choose option A.