Why Water Has a High Specific Heat Capacity

Water has one of the highest specific heat capacities of any common substance: $c = 4200$ J/(kg $^\circ$C). This means water absorbs or releases a large amount of energy for a small temperature change.

Practical consequences

Application	How water’s high $c$ helps
Car engine coolant	Water absorbs a lot of thermal energy from the engine without its temperature rising too quickly
Central heating	Hot water carries a large amount of energy through radiators to heat rooms
Coastal climate	The sea heats and cools slowly, moderating temperatures near the coast
Cooking	Water maintains a stable boiling temperature (100 $^\circ$C), providing even heating

Comparing materials

Material	Specific heat capacity / J/(kg $^\circ$C)
Water	4200
Aluminium	900
Copper	390
Iron	450
Oil	2000

For the same mass and energy input, copper heats up about 10 times more than water. This is why metals feel hot quickly but water takes a long time to boil.

Worked example

A coastal town and an inland town both receive the same amount of solar energy during the day. Explain why the coastal town has a smaller temperature rise.

The sea near the coastal town has a high specific heat capacity. It absorbs a large amount of energy for a small temperature rise. The land near the inland town has a lower specific heat capacity, so its temperature rises more for the same energy input.

Common errors and how to correct them

Saying water “holds heat well” without explaining what this means physically. State that water requires more energy per kilogram per degree to change temperature, so it absorbs more energy for a smaller temperature rise.

How to apply this in an exam

When asked about applications, name the specific role of water’s high specific heat capacity: it absorbs or releases a large amount of energy per unit mass per degree of temperature change.