Why Does Water Have a High Heat Capacity?

Water has a high heat capacity because a lot of heat energy is required to break the hydrogen bonds found in a molecule of water. Because the majority of heat energy is concentrated on breaking the hydrogen bonds, the water molecule itself heats up after the bonds are broken.

Once the hydrogen bonds in a water molecule are heated up enough to break, the additional heat energy can then be imparted to the water molecule itself. This additional heat energy then vibrates the water molecule, allowing it to bump into nearby water molecules to distribute the heat energy imparted by a heat source. However, the process of heat energy distribution is slow, as the vibrating water molecule must impart sufficient heat energy to break the hydrogen bonds in the surrounding water molecules. Once the heat source is removed from the water it cools down, but very slowly.