1. Gases are composed of a large number of particles that behave like hard, spherical objects in a state of constant random motion.
2. These particles move in a straight line until they collide with another particle or the walls of the container.
3. These particles are much smaller than the distance between particles. Most of the volume of a gas is therefore empty space.
4. Collisions between gas particles or collisions with the walls of the container are perfectly elastic. Energy can be transferred from one particle to another during a collision but the total kinetic energy of these particles after the collision is the same as it was before the collision.
5. The average kinetic energy of a collection of gas particles depends on the temperature of the gas and nothing else.

With these assumptions we can then explain the gas laws presented below.

• Boyle's Law Pressure x Volume is constant at constant temperature and number of particles
• Amonton's Law Pressure x (1/Temperature) is constant at constant volume and number of particles
• Charle's Law Volume x (1/Temperature) is constant at constant at constant pressure and number of particles
• Avogadro's Hypothesis Equal volumes of different gases contain the same number of particles
• Dalton's Law of Partial Pressures The total pressure exerted by a mixture of gases is equal to the sum of the partial pressure of each of those gases

Most of the time, you can use the combined gas law equation shown below to solve gas law problems:

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