Heat Capacity and Specific Heat

What Is Heat Capacity?

Heat is a very common term in science, which is defined as a form of energy transferred between two objects at different temperatures.

The heat capacity of a substance can be defined as the amount of energy required to raise its temperature by 1K.

In other words, heat capacity is also the capacity of a substance to absorb heat. Heat capacity depends on the mass of a substance making it an extensive property of the substance.

If sample A has a mass M and sample B has double the mass of sample A. To reach the same temperature, sample B would require double the heat energy compared to sample A. This is because sample B had double the mass of sample A and heat capacity depends on the mass of the substance.

The SI unit of heat is Joule per Kelvin or Joule per degree.

Use the formula below to calculate the heat capacity of a substance:

C = Q/ T

Where,

C – heat capacity

Q – heat energy supplied to bring change in temperature of the substance

T – rise in temperature

To understand the concept of heat capacity, take the example of heating iron. Iron rod heats and cools down quickly because it has very low heat capacity. However, water takes much more time to boil or cool down. This is because of the high heat capacity of water.

Hence, this example proves that heat capacity is also known as the ability of a substance to retain heat or cool down.

Heat capacity depends on the substance you are considering. It varies from substance to substance. Water has the highest heat capacity. However, you will have to consider the mass when talking about heat capacity. Even large water bodies take much more time to warm up than a small amount of water in a pan, bucket or tub.

What Is Specific Heat Capacity?

Specific heat capacity is the amount of heat energy required by a unit of substance to raise its temperature by 1K. It can also be defined as the amount of heat energy needed to add or subtract from a unit mass to change its temperature by 1 K.

Specific heat capacity, unlike heat capacity, is independent of the mass of a substance. There are two derived intensive heat capacities. They are:

1.     Molar heat capacity
2.     Specific heat capacity

Molar heat capacity is the heat energy required by a mole of a sample to change its temperature by 1K. It is the heat capacity per mole of a pure substance. CP and CV denote it. CP represents heat capacity at constant pressure, and CV represents heat capacity at constant volume. The SI unit of Molar heat capacity is J/K.Mol.

Specific heat of a substance is the amount of heat energy required by a sample unit to change its temperature. It is the heat capacity per unit mass of a pure substance. It is written as cp and cv, where the former is a constant pressure and the latter at constant volume. The SI unit of specific heat is J Kg-1K-1.

The formula to calculate specific heat is:

Q = mc𝛥 T

Where,

Q – heat energy

m – mass

c – specific heat capacity

𝛥T – change in temperature

Main Differences Between Heat Capacity And Specific Heat Of A Substance

The difference between heat capacity and specific heat confuses many students. This table will help you remember the difference and the definition of both.

Conclusion

 “Heat capacity” is a broad variable, but “specific heat” is a narrow one. The equation for “specific heat” includes a mass unit, as suggested by the International Standards of measurement. “Specific heat” is a better fit for theoretical and experimental purposes. The formula for heat capacity in SI units is C = Q / T, while the formula for specific heat is C = J / kg. K.

The main distinction between specific heat and heat capacity is that the specific heat is determined per unit mass of the substance.

Theoretically, both of these can be estimated using the formulas provided.