Specific heat capacity, change of state

Introduction 

In this article, we will be discussing the concept of specific heat capacity from NCERT chapter 11 Thermal Properties of Matter. We will discuss what specific heat and specific heat capacity are and the formula to calculate it and its unit of measurement. The form of energy transferred between two materials of different temperatures is called heat. 

Specific Heat 

• To raise the temperature by 1° C, the amount of heat per unit mass required is specific heat. 
• The formula to calculate specific heat is Q = mc∆T.
• Here, Q refers to the heat added, c denotes the specific heat, m is the mass, and ∆T refers to the change in temperature. 
• As per the Law of Dulong and Petit, the molar specific heats of most solids at room temperature and temperatures higher are always constant. 
• The Einstein-Debye model defines the behaviour of specific heat at a lower temperature, which states that specific heat drops at a lower temperature as the quantum processes become more significant. 
• The specific heat of water is 4.186 joule/gram ° C, which is equal to 1 calorie/ gram ° C. It is worth noting that the specific heat of water is higher than that of any other substance, even metal. 

Specific Heat Capacity 

• To raise the temperature of any substance by 1° C, the amount of heat energy required is called heat capacity. The amount of heat energy needed for a given substance depends upon its size and quantity. Therefore, heat capacity has an extensive property. 
• Alternatively, the heat capacity of a substance can be described as the temperature change that occurs when a certain amount of heat is absorbed or rejected by it.
• The heat capacity of a substance is defined as – S = QT. 

Here, Q refers to the amount of heat supplied to the substance to change its temperature. And S is the heat capacity. 

• We have observed that when an equal amount of heat is applied to different substances of equal masses, then the resultant change in temperature will not be the same. 
• Every substance has a unique value for the amount of heat. Therefore, it is implied that to change the temperature of unit mass by one unit, it can either absorb or reject heat. This unique value for the amount of heat is called the substance’s specific heat capacity. 

• The specific heat capacity is expressed as s = SM=1m△Q△T.

 Here, △Q stands for the amount of heat absorbed or rejected by the substance. S stands for the heat capacity of the substance.

m refers to the mass and △T refers to the change in temperature. 

• The property of a substance when a given quantity of heat is either absorbed or rejected by the substance that determines the change in the substance’s temperature is called specific heat capacity.
• Specific heat capacity refers to the amount of heat absorbed or rejected by a substance that changes its temperature by one unit. The specific heat capacity of a substance depends on the temperature and the nature of the substance itself. 
• The SI unit of specific heat capacity is J kg-1 K-1. 
• While specific heat capacity is expressed as SM=lm△Q△T, however, when the quantity of the substance isn’t defined as mass m in kg and is defined in terms of moles, the specific heat capacity is defined as C = S=1△Q△T. Here, C is the molar-specific heat capacity of the substance. Molar-specific heat capacity depends upon the nature of the substance and its temperature. 
• Molar-specific heat capacity of gases can be achieved by either keeping the volume or pressure constant. 
• SI unit of molar specific heat capacity is J mol-1 K-1. 
• Molar specific heat capacity at constant pressure refers to that heat transfer where the gas is kept under constant pressure. Cp denotes molar-specific heat capacity at constant pressure. 
• The molar specific heat capacity when the volume of the gas is kept constant during heat transfer is known as molar specific heat capacity at constant volume. Molar specific heat capacity at constant volume is denoted as Cv. 

Specific Heat Capacity Formula 

• There are two specific heat capacity formulas because of the way the quantity of a substance is defined. 
• The quantity of a substance is either defined in moles or as mass m in kg. 
• Specific heat capacity formula when the quantity of a substance is defined as mass m in kg is – S = SM=lm△Q△T. Here, m stands for mass. 
• Specific heat capacity formula (molar) when the quantity of a substance is defined as moles – C = S=1△Q△T. Here, C is the molar-specific heat capacity of the substance.
• Here, △Q stands for the amount of heat absorbed or rejected by the substance. 
• And △T refers to the change in temperature. 

Specific Heat Capacity Unit 

• The specific heat capacity unit, just like the formula, depends on the way the quantity of a substance is defined. 
• Therefore, the specific heat capacity unit differs when the quantity of a substance is defined as moles or as mass m in kg.
• Specific heat capacity unit when the quantity of a substance is defined as mass m in kg is J kg-1 K-1.

Specific heat capacity unit when the quantity of a substance is defined as moles is J mol-1 K-1.

Conclusion 

With this, we conclude our article on specific heat capacity. We hope that we were able to clarify and add to your knowledge on specific heat and specific heat capacity.