Structural Biochemistry/Unique Properties/Ability to Moderate Temperature

Water's Absorption of Heat
Water is able to resist temperature changes due to hydrogen bonding. Specifically, in order for water to increase in temperature hydrogen bonds must break giving rise to the relatively high boiling point of water. Conversely, hydrogen bonds must form before the temperature of water may be lowered. This property allows Earth's bodies of water to maintain temperatures by storing heat from the sun and releasing heat when cooler conditions arise.

High Specific Heat
Water has a high specific heat (the measure of heat energy required to increase the temperature of a unit quantity of a substance by unit degree) of 4.1813J/(g·K) and a high heat of vaporization (heat energy required to evaporate one unit quantity of a substance) of 40.65 kJ·mol−1. The consequence of this is that water is an excellent temperature regulator, being able to absorb and store a significant amount of heat before increasing in temperature and thus accommodate for environmental temperature changes and those caused by exothermic reactions within the body.

Evaporative Cooling
During the evaporation of water, fast-moving water molecules constantly collide and eventually escape from the surface. These escaping molecules carry heat along with their escape, causing the slower moving water molecules left behind to cool. Sweating is an example of this property, as the water molecules in sweat absorb the heat from the body and move faster, allowing them to vaporize.