If we add an ionic solute to water, will the specific heat of the water be increased or decreased?

I understand that the specific heat is a measure of how much energy we must add to water for the average kinetic energy of the water molecules to go up by a certain unit.

I also understand that hydrogen bonding is what limits the kinetic energy of the water molecules. This accounts for water's high specific heat.

However, when adding an ionic solute to water, such as $\ce{KI}$, we disrupt the hydrogen bonding. So we may expect the specific heat of a water solution to be lower than that of pure water.

On the other hand, there are ion-dipole interactions created, correct? These will act to at least partially counteract the specific heat depression, correct?

  • $\begingroup$ possible duplicate of physics.stackexchange.com/questions/2066/… $\endgroup$
    – DavePhD
    Jun 5, 2014 at 2:44
  • $\begingroup$ Actually that link does not bring up ion-dipole interactions; it is simply a discussion about one person's empirical findings. Could anyone shed some light on this? $\endgroup$
    – Dissenter
    Jun 5, 2014 at 14:20

1 Answer 1


From this website:

Every substance has its own specific heat and each phase has its own distinct value. In fact, the specific heat value of a substance changes from degree to degree, ...

It would mean that a solute in water would change the specific heat from plain water.

My guess is that if the density is greater than water, then the specific heat would be greater (because you are heating the water and the solute). To be certain, you would need to determine it for yourself.


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