Comment by garrettj100 on 06/12/2023 at 18:23 UTC

3 upvotes, 1 direct replies (showing 1)

View submission: Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary Science

• *Why** is water's heat capacity so high? I understand there are a lot of *modes* for liquid water to accept energy, but what makes water exceptional? There are plenty of larger molecules[1] than water, and while I certainly don't know all the vibrational modes I would expect they'd have *more*, right? What's the deal?

1: https://s3-us-west-2.amazonaws.com/courses-images/wp-content/uploads/sites/1094/2016/11/03154650/OSC_Microbio_07_01_isomers.jpg

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Comment by Flannagill at 06/12/2023 at 22:55 UTC

9 upvotes, 1 direct replies

As you correctly pointed out, water can absorb heat due to its many modes. This of course isn't what makes water unique, many other compounds can do this even better as you pointed out.

To answer your question we don't have to think about modes or statistical thermodynamics, but think of it like this: The intermolecular bonds between water (hydrogen bonds) are quite strong (for intermolecular bonds) and can take a lot of heat before breaking. Because water exists of two Hydrogen attached to one oxygen, it's potential for forming these bonds relative to the small volume of one molecule is enormous.