What is the kinetic theory of gases

Kinetic gas theory

We will deal with the kinetic theory of gases in this article. We will explain to you what is meant by the kinetic gas theory and provide you with formulas and examples. This article belongs to the field of thermodynamics.

The kinetic gas theory explains the gas laws and the properties of gases through the motion processes of their particles. The most important statements of the theory are:

  • The particles of a gas are constantly in disorderly motion
  • The particles do not exert any forces on one another as long as they do not touch one another
  • Collisions of the particles with the vessel wall are elastic collisions and cause the gas pressure

We will now take a closer look at the points mentioned in the following.

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Kinetic Gas Theory: Disordered Motion

The kinetic theory of gases implies that the particles of a liquid are in disorderly motion. This is also known as Brownian molecular motion, named after the Scottish botanist Robert Brown. It discovered the heat movement of particles in liquids. The particles perform a completely random "zigzag movement". Brown observed under the microscope how pollen made irregular twitching movements in a drop of water. The following graphic shows the arrangement of the particles in different aggregate states.

The particles of a gas have different speeds. In principle, one can say: the higher the temperature of the gas, the faster the particles move.

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Kinetic gas theory: forces

Apart from that, it is assumed that the particles do not exert any forces on one another as long as they do not touch one another. In addition, the following applies: collisions of the particles with the vessel wall are elastic collisions and cause the gas pressure.

The gas pressure is created as the sum of all forces acting on a vessel wall by a gas. If a gas particle hits a wall, they exchange an impulse. The momentum transfer depends on the kinetic energy of the gas particle. It also depends on the direction in which the particle hits the wall. For many particles these momentum transfers add up to a total force.

Kinetic gas theory: formulas

The formulas for the kinetic gas theory establish relationships between the quantities energy, mass, speed, pressure, number of particles and volume for gases.

Mean kinetic energy:

Where:

  • "E.KIN"the mean kinetic energy of the particles in Newton meters [Nm]
  • "m" is the mass in kilograms [kg]
  • "v" is the mean speed of the particles in meters per second [m / s]

Example:

The mass of a gas is 5kg, the average speed is 480m / s. What is the mean kinetic energy?

Basic equation kinetic gas theory:

Where:

  • "p" the pressure in Newtons per meter [N / m]
  • "V" is the volume in cubic meters [m3 ]
  • "N" is the number of particles, without a unit
  • "E.KIN"is the mean kinetic energy of the particles in Newton meters [Nm]

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