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So far our discussion has been about the property and behaviour of a gas on a big (macro) scale i.e. pressure and volume, which involve billions of atoms or molecules.

Kinetic theory takes the view that if you really want to understand what's going on you need to look at how individual atoms are behaving.

Ideal gases and Internal Energy.

Normally we consider the internal energy of a substance to be made up of two components - Ek and Ep.

The Ek is the vibration, rotation or translation of the atoms.

The Ep is due to the interaction of one atom and its neighbours.

The impact of these two components on the temperature and state of the substance they belong to is discussed at the start of the 'Thermal Properties' section.

Once again as with our earlier gas work, we need to imagine an Ideal Gas that behaves in a perfect way. We've already stated that an Ideal Gas is one that perfectly obeys the Gas Laws. Here's something else about Ideal Gases.

An Ideal Gas is one in which all its internal energy is in Ek form. i.e. it has no Ep. How can you justify this? Well Ep is as a result of one atom exerting a force on its neighbours. In ideal gases, each atom acts independently. It is unaware of the fact that any other atoms exist (except during collisions - but they only last for an instant!)