Specific Heat Capacity

When heat is applied to any substance, solid, liquid, or gas, it absorbs the heat energy. The molecules gain more energy and start vibrating or moving from their original position until the substance changes its state. As the substance absorbs heat energy, its temperature gradually rises. This phenomenon is specific heat, and it varies from one material to another. However, for describing different aspects, the specific heat of water is considered the reference since it is the highest of all substances. The concept of specific heat capacity has several applications, starting with judging the thermal capacity, thermal energy storage, etc.

What is Specific Heat Capacity? 

Specific heat capacity is the amount of heat absorbed by a body to increase the temperature per unit degree and mass within a thermodynamic system. In any thermodynamic system, heat exchange occurs till it reaches thermal equilibrium in an ideal case. 

• For example, if we consider a system A whose temperature is T and that of the surrounding is T’.

• If T<T’, then heat energy will flow from the surrounding into the system A. 

• The molecules present in system A will continue to absorb the heat energy to increase the overall temperature. 

• The specific heat capacity is the amount of heat energy absorbed per unit mass of system A to increase the temperature per unit. The term is defined as “c”. 

The Formula of Specific Heat Capacity

From the definition, we can derive the formula of specific heat capacity step by step. 

• Let us consider a substance with mass M. 

• The initial temperature of the substance is Ti, and the final temperature (after absorbing heat) is Tf. 

• Let us assume that the heat energy absorbed is Q. 

• Now, the heat energy absorbed is directly proportional to the mass and temperature of the concerned substance. Therefore, the physical expression can is: 

Q ∞ m(Tf-Ti)

Or, Q ∞ mT

To remove this proportional sign, we introduce a constant as

Q = cmT

Here, the constant c is the specific heat capacity of a substance. We can write the formula of specific heat using the algebraic mathematical concept: 

cmT = Q

c = Q/mT 

If the mass of the object is 1 kilogram and the temperature has increased by 1˚C, then we can change the specific heat capacity equation as: 

c = Q 

Unit of Specific Heat Capacity 

Specific heat capacity of water or any other substance depends on the amount of heat absorbed, the mass, and the temperature difference between the initial and final values. 

We can define as the formula of specific heat capacity:

c = Q/mT

Q being the heat energy has the SI unit of Joules or J, m is the mass with an SI unit of Kg, and T is the temperature with an SI unit K. Therefore, the unit of specific heat capacity is: 

c = J/kgK

Specific Heat Capacity of Water- Explanation

• The specific heat capacity of water is the highest among all other substances that can absorb and lose thermal energy. 

• Its constant value is about 4182 J/kg˚C. 

• It means that increasing water temperature by 1˚C of unit mass is 4182 Joules. 

• This valuation shows how much energy water needs to raise the temperature by only one unit degree. 

• When we consider 10 kilograms of mass, the heat energy required to increase the temperature by a unit degree is 41820 Joules. 

• This is why it needs such a massive amount of heat energy to reach the boiling point of 100 ˚C. 

Real-life Advantages of High Specific Heat Capacity of Water 

Land and sea breeze

• During the daytime, both land and water will absorb heat energy. Since the specific heat capacity of water is more than that of the land, it will continue to absorb more energy but won’t get overheated. 

• On the other hand, land can absorb little heat and therefore, the air above heats up quickly. It rises, thereby creating a vacuum. The cold air over the sea rushes in to fill the void, known as the sea breeze. 

• Water takes more time to cool down at night due to its high specific heat capacity, but land cools down faster. As a result, the air above the sea will remain warm and rise, creating a vacuum. The cold air over the land rushes in to fill the gap, known as the land breeze. 

Conclusion 

The specific heat of water is the highest, so the value is a reference for many physical applications in thermal physics. This is why water needs to absorb a considerable amount of heat before its temperature reaches 100 ˚C and gets converted into vapours. The specific heat capacity is a constant value that differs with every substance. It is the amount of heat absorbed per unit mass for increasing its temperature per unit degree. We also consider specific heat capacity to establish thermal equilibrium.