I am curious about the effect that adding potassium chloride to water in varying concentrations has on its specific heat capacity. I have been unable to find any online information about this? Theoretically, would one expect a linear relationship or something different? Furthermore, how would this change if we added another soluble material to water? Any insights on the same would be much appreciated.
1 Answer
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The addition of a salt, such as $\text{KC}\ell$, decreases the specific heat capacity of the water. This is a well known colligative property.
Quoted from this answer (under the Creative Commons License):
When we heat a sample of water, the energy goes into raising the energy levels of its various vibrational, rotational, and translational motions.
When we dissolve $\text{NaC}\ell$ in water, the ions are held in a rigid cage of water molecules.
The cage is rigid enough so that the motions of its molecules are "frozen out".
The added heat cannot go into increasing the energy of these motions, so it goes into increasing the energies of the other water molecules in the solution.
It takes less energy to activate these molecules, so the specific heat of the water decreases.
The greater the concentration of $\text{NaC}\ell$, the lower the specific heat capacity of the solution.
Now, regarding the relationship between the salt concentration (salinity) and specific heat capacity, we can experimentally deduce that their relationship is, in fact, linear. Relevant articles here and an experiment here.
You can find more related information at this Encyclopædia Britannica article.
