At low pressures, most gases obey the following assumptions:

1. The gas consists of a large number of particles.
2. The particles within the gas move randomly and their motion can be described using Newton’s laws.
3. The distances between the particles is on average much greater than the size of the particles.
4. The particles do not attract or repel each other and only interact with other particles or their surroundings through elastic collisions.

This allows us to create a relatively simple model for low pressure gases known as the ideal gas model.  We can use this model to determine the behavior of an ideal gas as it is taken through a series of thermodynamic processes.