Chapter 6: Gases

By the end of this chapter you will be able to:
  • Describe and quantify a gas sample (pure and mixture) using the following variables: number of moles, volume, temperature, total and pressure.
  • Describe and quantify partial pressure for a component in a gas mixture.
  • Describe the behaviour of ideal and real gases using the kinetic molecular theory of gases.
A photograph shows about twenty colorful hot air balloons at varying stages of inflation. Some are deflated, while others are inflated. Three of the balloons are off the ground and are visible against a bright blue sky.
The hot air inside these balloons is less dense than the surrounding cool air. This results in a buoyant force that causes the balloons to rise when their guy lines are untied. (credit: modification of work by Anthony Quintano)

We are surrounded by an ocean of gas—the atmosphere—and many of the properties of gases are familiar to us from our daily activities. Heated gases expand, which can make a hot air balloon rise or cause a blowout in a bicycle tire left in the sun on a hot day.

Gases have played an important part in the development of chemistry. In the seventeenth and eighteenth centuries, many scientists investigated gas behavior, providing the first mathematical descriptions of the behavior of matter.

In this chapter, we will examine the relationships between gas temperature, pressure, amount, and volume. We will study a simple theoretical model and use it to analyze the experimental behavior of gases. The results of these analyses will show us the limitations of the theory and how to improve on it.

Sections in this chapter:

  1. The Ideal Gas Law
  2. Gas Behaviour: Kinetic-Molecular Theory
  3. The Boltzmann Distribution and Gases
  4. Kinetic Molecular Theory and Gas Pressure
  5. Standard Conditions
  6. Non-Ideal Gas Behaviour