Accessible #56

Water has more than twice the specific heat capacity of ice or steam

The specific heat of liquid water is anomalously high compared to its solid and gaseous phases.

Scientific Explanation

Comparing the specific heat capacity of water across its three phases reveals a dramatic jump: liquid water requires 4.18 joules per gram per kelvin to warm by one degree, while ice needs only 2.1 and steam only 2.0 joules. Liquid water thus has more than double the heat capacity of its solid and gaseous forms.

The reason lies in hydrogen bonds. In liquid water, a dynamic network forms in which bonds constantly break and reform. A portion of the added heat goes not into raising the kinetic energy of molecules (which would register as a temperature increase) but into breaking and rearranging hydrogen bonds. In ice, molecules sit in a rigid crystal lattice, and in steam, virtually no hydrogen bonds exist — in both cases, this extra energy-absorbing mechanism is absent.

Specific Heat Capacity of Ice, Liquid Water, and Steam Bar chart comparing the specific heat capacity of ice (2.1 joules per gram kelvin), liquid water (4.18 joules per gram kelvin), and steam (2.0 joules per gram kelvin). Liquid water has more than double the specific heat of its other phases. Specific Heat (J g⁻¹ K⁻¹) 0 2.5 4.5 2.1 Ice 4.18 Liquid Water 2.0 Steam Liquid water — more than 2× ice or steam
Specific heat capacity across the three phases of water. Liquid water exceeds both ice and steam by more than a factor of two.

Everyday Relevance

This property makes water an ideal heat store. Heating systems transport warmth using water because it can absorb far more energy per kilogram than almost any other liquid. Our bodies benefit too: blood, which is over 90 percent water, transports heat efficiently from the core to the skin, keeping body temperature stable.

In the kitchen we experience the effect daily: a pot of water takes a surprisingly long time to boil — but it also holds its heat for a long time. This is precisely what makes water such an effective medium for cooking, heating, and cooling.