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

Question

Ellie Andrews · Accepted Answer

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!

Olivia Anton · Answer

undefined Water takes longer to heat up or cool down compared to many other substances due to its high specific heat capacity. This property is a result of hydrogen bonding between water molecules, which requires a significant amount of energy to break. As a result, water can absorb large amounts of heat energy without experiencing a significant increase in temperature, and it releases heat slowly when cooling down. Additionally, water's high latent heat of vaporization and fusion contribute to its slow heating and cooling rates, as these processes require the absorption or release of substantial amounts of heat energy without a corresponding change in temperature.