ABSTRACT
This chapter discusses the experimental behaviour of real gases, and develops ideal gas theory to compare its predictions with the experimental results. By juxtaposing predictions and experimental results, it shows both the successes and the failures of ideal gas theory, and explores how the theory can be developed to model the properties of real gases more closely. The most striking property of gases is their ability to expand to fill any container. In other words, a fixed number of gas molecules has no fixed volume and hence no fixed density. Air is a mixture of several gases whose relative abundances vary slightly from place to place. The heat capacity of a gas is defined as the limiting value of the ratio of the heat energy input to the resulting temperature rise. The value obtained for the ratio of the heat energy input to the resulting temperature rise depends on the conditions under which the heat input is made.
