The specific heat capacity of a substance refers to the energy required to increase the temperature of one gram of that substance by one degree Celcius. Specific heat capacity is often represented in calories (cal), grams (g), and degrees Celsius (^oC), but can also be expressed in joules (J), kilograms (kg), and Kelvin (K), among other units.

For example, increasing the temperature of one gram of water by 1°C requires one calorie of heat energy and can be written as 1 cal/g-°C, or 4186 J/kg/K. Water has a high specific heat capacity. It absorbs a large amount of heat to increase its temperature and similarly releases a lot of heat when it cools down. Therefore, it takes significant time for water to heat or cool down.

On the other hand, metals have a low heat capacity and thus heat up quickly and cool down quickly. For example, solid gold has a specific heat capacity of ~0.03 cal/g/°C or 129 J/kg/K, which is much less than water.

Water has a high specific heat

When water is boiled, a high amount of energy is absorbed to break the hydrogen bonds between the water molecules. This results in the random movement of water molecules. Similarly, when the water cools down, hydrogen bonds start forming between the water molecules when the water cools down, bringing them closer. An enormous amount of heat is released in this process.

Moderation of environmental temperatures

The high heat capacity of water helps modulate extreme environmental temperatures. Towns near large bodies of water have more minor temperature changes daily and seasonally. During the day, the nearby water absorbs heat energy, cooling the surrounding land. The water releases its heat energy at night, keeping the area warmer. Towns away from large bodies of water can experience large swings in daily and seasonal temperatures. Since sand and rocks have lower heat capacities, they heat up quickly during the day and rapidly release heat at night.