What is the specific heat of water?

The specific heat capacityalso known as specific heat or specific heat capacityis a property of substances related to the amount of energy needed to increase their temperature.

One of the most significant characteristics of water is that it has a very high specific heat capacity. This means that to increase the temperature of water, it needs to absorb a lot of heat per unit mass.

To get an idea, for 1 kg of water to increase its temperature by 1 ºC, 4184 J (joules) are needed, while it only takes 385 J to do the same with 1 kg of copper or 130 J for lead.

What is specific heat?

Specific heat is based on the concept of heat capacity, or amount of thermal energy needed to change the temperature of a substance. Heat capacity is defined as an extensive property of matter, and therefore it is a property that depends proportionally on the mass or amount of matter.

Specific heat capacity, better known as specific heat, is defined as the heat capacity for a given unit mass. In the International System it is defined exactly as the heat capacity for 1 kilogram of substance and for a temperature rise of 1 degree Kelvin.

The heat capacity is measured in Joules per Kelvin (J/K) and its symbol is C:

heat capacity formula

Specific heat capacity is measured in J/(K kg). If the temperature change of a homogeneous substance does not imply a change of state, the relationship of that temperature change, the mass and the heat exchanged is usually expressed as follows:

specific heat formula

Where:

  • Q It's the heat
  • m mass,
  • ΔT the temperature change
  • c specific heat

Thus, the specific heat can be obtained as:

Specific Heat Formula 2

The specific heat is different depending on whether the volume of the substance remains constant (isochoric specific heat) or the pressure is kept constant (isobaric specific heat), although in practice this difference is mainly used when working with gases.

Specific heat value of water

Under standard conditions, one kilogram of water needs 1 kilocalorie for its temperature to increase 1 ºCthat is, 1 kcal/°C kg, which is equivalent to 4184 J/(K kg) in the international system.

The specific heat of water is higher than any other common substance. If you put a basin with water in the summer in full sun, it will get hot and warm, but you won't be able to cook some eggs in it, but if you leave a metal bar you probably won't be able to catch it, it will burn.

The high specific heat of water is due to Hydrogen bondsa type of molecular interaction that occurs between water molecules and that is so strong that it is necessary to supply a lot of energy to make them vibrate and increase their temperature.

Importance in weather regulation

The fact that water has such a high heat capacity is not just a curious fact, it is a very important property that makes a significant contribution to weather and climate regulation.

Having such a high specific heat, large masses of water regulate extreme fluctuationsespecially temperature.

In a lake, for example, the high specific heat keeps the mean temperature of the water relatively constant between day and night. This same effect can be carried to larger scales. Thus, the oceans, seas and lakes regulate the fluctuations and ranges of temperature in large regions.

It is a fundamental meteorological and environmental factor in coastal and insular areas. Towns and cities near large bodies of water warm more slowly and also cool more slowly, so they experience fewer fluctuations and less extreme temperatures.

Thanks to the high specific heat of water, both winters and summers are milder than inland areas but at the same latitude. Taking into account that the oceans cover 70% of the planet's surface, this effect is undoubtedly essential to regulate the weather worldwide.

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