Question

How does salt change the specific heat capacity of water?

Answer 1

Hint: When pure water is heated, it takes time to cool down but when any solute like salt, sugar is dissolved in the water and heated it does not take much time to get cooled as the water molecule traps the solute particle in the solution.

Complete step by step answer:
The specific heat capacity is defined as the amount of heat required to raise the temperature of one kilogram of substance by one kelvin. The unit of specific heat capacity is $JK{g}^{-1}{K}^{-1}$.
When the water is heated, the energy of the water rises with the rise in energy level of its various rotational motion, vibrational motion and translational motion.
When the sodium chloride NaCl is dissolved in the water, the ions are held together by a rigid cage of water molecules. The cage of water molecules is so rigid that as a result the movement of the salt molecule is frozen. The heat added cannot go on increasing the energy of the molecules so it starts to increase the energy of the other water molecule.
As, it requires less heat to activate the molecule, so the specific heat of the water decreases. So, the greater is the concentration of the sodium chloride dissolved in the water, the lower will be the specific heat capacity of the water. In other words increasing the concentration of salt in water decreases the specific heat capacity of water.

Note:
Water has the highest heat capacity of all the material present in the earth. Due to this water acts as a thermal buffer, resisting temperature changes as it loses or gains the heat energy.