 # Principle Of Calorimetry

The Universe comprises energy and matter where matter includes particles, namely molecules and atoms. Moreover, the molecules and atoms with the help of energy can move invariably. So, their motion can either be that of colliding with each other or moving forward and backwards.

As a result of this motion between atoms and molecules, heat energy is formed, which is one of the fundamentals of the principles of calorimetry. Furthermore, thermal energy is present everywhere – in a human body, in volcanoes and even in the coolest spaces. It is transferable from one body to another body.

This heat flow that takes place within physical processes and chemical reactions is measurable. Additionally, the procedure of measuring heat is termed as calorimetry.

### What Is Calorimetry?

To define calorimetry, it can be said that it is an act of quantifying change in thermal energy of an object. Some of the vital highlights related to calorimetry are as follows.

• The temperature of a body or an object determines the heat amount present in that body.

• Temperature and heat energy are directly proportional to each other. So, this means that more the amount of heat energy more is the temperature of a body.

• To evaluate the loss and gain of thermal energy, an object’s temperature is measured prior and after the transfer of heat. Hence, this temperature difference ascertains the heat change of a body.

For example:

Let us consider a hot cup of coffee or chilled ice cream, which are kept at room temperature. Eventually, after an hour or two, the coffee will cool down, and the ice cream will melt. This change happens because the coffee releases heat energy, and it’s temperature reduces. On the other hand, the ice cream’s temperature rises as it absorbs heat from the atmosphere.

Notably, the process of calorimetry is executed using a calorimeter. A calorimeter is a tool that measures either the quantity of heat energy gained or released, or specific heat capacity.

### What Is The Principle Of Calorimetry

In a calorimeter, two forms of matter (desirably a liquid and a solid) are situated in contact with one another. Moreover, both bodies have distinct temperatures. Due to this arrangement, heat energy gets transferred from an object having greater temperature to an object having lesser temperature.

However, heat flow continues until a state of thermal equilibrium is achieved between the bodies. The principle of calorimetry signifies the “law of conservation of energy.” Hence, this statement means that total amount of heat absorbed by the cold object is equal to the total amount of heat released by the hot object.

### Formula Related to Calorimetry

The basic concept of calorimetry is as follows.

Heat released by hot object = Heat absorbed by cold object

The transfer of heat is evaluated with the help of a formula, which is as follows

Q = mCΔT

Where, Q = Entire heat energy (J)

m = Mass of an object or body (g)

C = Specific heat capacity (J/gm K)

ΔT = Change in temperature (°C)

(Fact: 4.1813 J/gm K is the specific heat capacity of water)

### Numericals on Principles of Calorimetry

(i) What is the amount of heat needed to change 1g of water by 40°C. Provided that C of water is 4.2 J/gm K.

Solution: C= 4.2 J/gm K; m= 1g; ΔT= 40, then

According to the equation Q= mCΔT,

Therefore, Q= 1 X 4.2 X 40= 168 Joules.

(ii) 1000J of heat is applied to a mass of lead 0.5kg to change its temperature from 20°C to 40°C. Determine its heat capacity.

Solution: Q= 1000J; m= 0.5kg; ΔT= (40-20)°C= 20°C, then

C= 1000/(0.5X20); C= 100 J/kg K.

Do It Yourself

1. The Study of Calorimetry is Based on Which Law?

(a) Law of Kinetic Energy (b) Joule’s Law (c) Law of Conservation of Energy (d) None

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1.What are the Kinds of Calorimeter?

Ans. Some different kinds of calorimeters are reaction calorimeters, adiabatic calorimeters, differential Scanning calorimeters, Constant Volume calorimeters, etc.

2. What Equation is Used in Calorimetry?

Ans. The equation for calorimetry is Q = mc∆T, where Q= heat evolved, m= mass, c= specific heat capacity and ∆T= change in temperature.

3. What is the Principle of Calorimetry Class 11?

Ans. The principle of calorimetry states that heat loss from one object is equivalent to heat gain by another object.