Question

Why does water take so long to heat up or cool down?

Answer 1

Consider the intermolecular forces between molecules of water.

There is a very strong `delta^+` on the hydrogens, and a very strong `delta^-` on the central oxygen. These very strong dipoles are attracted to the opposite partial charge in other molecules, such that (pure) water at a molecular level will look something like,

(that's from my biochemistry book, this stuff still matters!)

Hence, all of these relatively strong intermolecular forces need to be overcome in order for the kinetic energy of the molecules (over a standard distribution) to increase, hence increasing the "temperature".

To be sure, the rate of heat energy addition to the system (if constant) will take longer than if we were heating petroleum ether in the lab. That's why I didn't like general chemistry lab, we always had to boil water!