There are various **branches of physics** and various types of topics in physics taught in class 11. One such topic is the Kinetic Theory of Gases Class 11. The kinetic theory of gases demonstrates the 3 visible features of a gas in terms of the microscopic nature of atoms and molecules forming the gas. Generally, the physical characteristics of solids and fluids can be distinguished based on their area, form, mass, volume, etc. In the case of gases, they have no distinct shape, size, and mass and volume are not directly calculable. Here, in this blog, we discuss all details about the kinetic theory of gases class 11.

**Must Read: Class 11 Physics Chapter 7 – System of Particles and Rotational Motion**

##### This Blog Includes:

- What is the Kinetic Theory of Gases?
- Ideal Gas
- Kinetic Theory and Gas Pressure
- Boyle’s Law
- Charles’s Law
- Gay Lussac’s Law (or Pressure Law)
- Equation of State of An Ideal Gas
- Avagadro’s Law
- Graham’s Law of Diffusion of Gases
- Dalton’s Law of Partial Pressures
- Kinetic Interpretation of Temperature
- Degrees of Freedom
- Law of Equipartition of Energy
- Mean Free Path
- Brownian Motion

## What is the Kinetic Theory of Gases?

The kinetic theory of gases class 11** **chapter** **illustrates the **molecular structure** of the gas in terms of the abundance of submicroscopic particles. The theory also demonstrates that gas pressure occurs because of the particles striking against each other and the surface of the vessel. The kinetic theory of gases also describes characteristics such as temperature, coherence, and thermal conductivity.

The^{ }**importance of the kinetic theory** is that it assists in forming a relationship between the perceptible attributes and the microscopic phenomenon. In other words, the kinetic theory of gases also assists us to analyze the behavior of the molecules. Usually, the molecules of gases are constantly in motion and they conduct strikes against each other and the surfaces of the vessels.

The kinetic theory was stated in the 19th century by **Maxwell, Boltzmann, **and others. Kinetic theory illustrates the reaction of gases based on the view that the gas consists of swiftly flowing atoms or molecules.

## Ideal Gas

Next in the kinetic theory of gases class 11, we move on to ideal gas. An ideal gas rigidly follows gas fundamentals such as **Boyle’s law, Charle’s law, Gay Lussac’s law**, etc.

An ideal gas has the succeeding features:

- Molecules of an ideal gas is a
**point mass**with**no geometrical dimensions.** - There is
**no force of attraction or repulsion**amidst the molecules of the gas.

## Kinetic Theory and Gas Pressure

The pressure of a gas is the result of continuous bombardment of the gas molecules against the walls of the container. According to the kinetic theory of gases class 11, the pressure exerted by an ideal gas is given by:

Where is the density of the gas and c^{-2 }is the mean square speed of the gas molecules. If a container has n molecules each of mass m, then

**P=13c ^{-2}**

where V is the volume of the container.

## Boyle’s Law

As per Boyle’s law in the kinetic theory of gases class 11, the **volume (V)** of a definite mass of a gas is** inversely proportional** to the **pressure (P)** of the gas, presented the temperature of the gas is maintained constant.

**i.e., V∝ 1P or PV = constant**

## Charles’s Law

Next, we move on to Charle’s Law in the kinetic theory of gases class 11. As per Charles’s law in the kinetic theory of gases class 11, the **volume (V)** of a provided mass of a gas is **directly proportional** to the** temperature** of the gas, given the pressure of the gas continues to be constant.

**i.e., V∝ T or VT= a constant V _{1}T2= V_{2}T2**

## Gay Lussac’s Law (or Pressure Law)

Moving on to the kinetic theory of gases class 11, we have Guy Lussac’s Law. As per the law of Gay Lussac or the Pressure Law, the **pressure P** of a provided mass of a gas is** directly proportional **to its **absolute temperature T**, given the volume V of the gas is kept constant.

**I.e., P∝ T or ****P****T****= a constant ****P**_{1}**T1****=**** ****P**_{2}**T2**

## Equation of State of An Ideal Gas

Next, the kinetic theory of gasses class11 talks about the equation of the state of an ideal gas. The relation among pressure P, volume V and absolute temperature T of a gas is called its **equation of state**. The equation of state of an ideal gas

**PV = nRT**

where *n* is the number of moles of the contained gas and* R* is the molar gas constant which is alike for all gases and its value is

**R = 8.315 JK-1 mob-1**

## Avagadro’s Law

Avogadro’s Law is also important in the kinetic theory of gases class 11. Equal amounts of all gases under **standard temperature and pressure**, contain the same number of molecules comprising **6.023 x 1023 **molecules.

## Graham’s Law of Diffusion of Gases

We further move on to Graham’s Law of Diffusion of Gases in the kinetic theory of gases class 11. It says that the **rate of diffusion** of a gas is **inversely proportional** to the **square root of the density of the gas**.

**i.e., r∝ 1**

Therefore, the denser the gas, the more passive is the rate of diffusion.

## Dalton’s Law of Partial Pressures

Dalton’s Law of Partial Pressures is also an important topic in kinetic theory of gases class 11. As per this law, the **net pressure** applied by a mix of non-interacting gases **is equivalent**

**to the sum of their pressures**.

i-e., P = P1 + P2 + ————-Pn

**The mean (or average) speed of molecules** of a gas is defined as the arithmetic mean of the speeds of gas molecules.

**I.e., mean speed, **_{mean }**= **_{n}**n****= ****8KBT/****m**

Where *m *is the mass of 1 molecule of given gas and *T*= temperature of the gas.

**The root mean square speed of gas** molecules is defined as the square root of the mean of the squares of the speeds of gas molecules.

**The most probable speed** of gas molecules is defined as the speed which is possessed by the maximum number of molecules in a gas.

## Kinetic Interpretation of Temperature

The **total average kinetic energy** of all the molecules of a gas is** proportional** to its **absolute temperature (T)**. Thus, the temperature of a gas is an estimate of the average kinetic energy of the molecules of the gas.

**U = 3/2 RT**

As per this understanding of temperature, the **average kinetic energy U is zero at T = 0**, i.e., the movement of molecules halts altogether at absolute zero.

**Also Read: Physics Syllabus For Class 11**

## Degrees of Freedom

The entire number of free coordinates needed to define the location of a molecule or the number of autonomous forms of motion achievable with any molecule is called the** degree of freedom.**

**Mono-, di-, and polyatomic (N) **molecules have, 3,5 or (3 N-K) number of degrees of freedom where K is the number of limitations.

## Law of Equipartition of Energy

For a dynamic system in thermal equilibrium, the energy of the system is evenly distributed amongst the different **degrees of freedom** and the energy linked with every degree of freedom per molecule is** 1/2 kT**, where k is Boltzman constant.

## Mean Free Path

**The mean free path** of a molecule in a gas is the average distance covered by the molecule between 2 consecutive collisions.

**Smaller the number of molecules**per unit volume of the gas,**the larger is the mean free path.****Smaller the diameter**, the**larger is the mean free path**.**Smaller the density**, the**larger is the mean free path**. In the case of vacuum,**ρ = 0, λ —>∞****Smaller the pressure**of a gas, the**larger is the mean free path**.**Higher the temperature**of a gas, the**larger is the mean free path**.

## Brownian Motion

The last and another important portion in the kinetic theory of gases class 11 is the Brownian Motion. The constant arbitrary movement of microscopic particles suspended in air or any liquid is called **Brownian or microscopic motion.**

Brownian suspended motion in the air or any liquid is witnessed in various fluids. Brownian motion is because of the uneven bombardment of the dissolved particles by the molecules of the encircling medium.

**Explore: Class 11 Physics Chapter 3 – Motion in a Straight Line**

We hope our notes on the Kinetic Theory of Gases Class 11 notes helped you understand the essential concepts covered in this chapter. Still unsure about which stream to choose after Class 12? Our **Leverage Edu** experts are here to guide you in selecting the right stream of study to make sure that you make an informed decision. Sign up for a free session with us now!