What is the kinetic molecular theory of gases? What is its purpose?

May 24, 2018

The kinetic molecular theory is a set of postulates that we assume to be true for gases. We use it in order to describe the behaviour of gases.

Explanation:

When we talk about kinetic molecular theory (KMT), we're really talking about a set of five major postulates which we assume to be true when describing the behaviour of gases.

These postulates are, essentially:

1. Gas particles have negligible volume. This means that gases are mostly made up of empty space.
2. Gas particles do not attract or repel each other unless they collide.
3. When gas particles do collide (with either themselves or the walls of the container), these collisions are elastic. This means that no energy is gained or lost in them.
4. Gas particles move randomly.
5. The energy of these particles depends only on the temperature.

It is important to remember that these are only postulates which we assume to be true!
Gases do not perfectly follow the KMT in real life.

The reason we use the KMT, despite gases not perfectly following it in real life, is because it helps us understand and describe the behaviour of gases.
It also helps us write equations to describe these behaviours of gases—one such equation is the Ideal Gas Law, which states that $p V = n R T$.