## Ideal gas and gas laws

IDEAL GAS

An ideal gas is one that obeys all the assumptions of the kinetic theory of matter. A real gas behaves like an ideal gas, except at high pressures and low temperatures. This will be discussed in more detail later in this tutorial

We are surrounded by gases in our atmosphere which support and protect life on this planet.

In this tutorial, we are going to try to understand more about gases, and learn how to predict how they will behave under diﬀerent conditions.

The kinetic theory of matter was discussed earlier. Please check the tutorial section for more on Kinetic theory of matter.

However before we proceed  we will quickly take a review of the kinetic theory of matter.This theory is very important in understanding how gases behave.

### A review of the kinetic theory of matter

The main assumptions of the kinetic theory of matter are as follows:

• Matter is made up of particles (e.g. atoms or molecules)
• These particles are constantly moving because they have kinetic energy. The space in which the particles move is the volume of the gas.
• There are spaces between the particles
• There are attractive forces between particles and these become stronger as the particles move closer together.
• All particles have energy. The temperature of a substance is a measure of the average kinetic energy of the particles.
• A change in phase may occur when the energy of the particles is changed.

The kinetic theory applies to all matter, including gases. In a gas, the particles are far apart and have a high kinetic energy.

They move around freely, colliding with each other or with the sides of the container if the gas is enclosed.

The pressure of a gas is a measure of the frequency of collisions of the gas particles with each other and with the sides of the container that they are in.

If the gas is heated, the average kinetic energy of the gas particles will increase and if the temperature is decreased, so does their energy.

If the energy of the particles decreases signiﬁcantly, the gas liquiﬁes.

Deﬁnition: An Ideal gas or perfect gas is a hypothetical gas that obeys all the assumptions of the kinetic theory of matter. In other words, an ideal gas would have identical particles of zero volume, with no intermolecular forces between them. The atoms or molecules in an ideal gas would also undergo elastic collisions with the walls of their container.

Deﬁnition:  Real gases behave more or less like ideal gases except under certain conditions e.g. high pressures and low temperatures.

There are a number of laws that describe how gases behave. It will be easy to make sense of these laws if you understand the kinetic theory of gases that was discussed above.