ChE102The Kinetic-Molecular Theory of Gases Petrucci et. al. 6.7 pg. 1 of 3 Postulates of the kinetic-molecular theory of gases: A gas is composed of a very large number of molecules in ceaseless random straight-line motion. These molecules are separated by a large distance relative to their own size. The molecules behave like hard spheres that undergo perfectly elastic collisions with one another and the walls of the container. There are no forces of attraction or repulsion between the molecules. Using these postulates we can develop a model that predicts gas behaviour in terms of measurable properties such as temperature, pressure and volume. Imagine a cube containing gas molecules. We’ve discussed earlier that pressure arises from theforce imposed by molecules colliding with the walls of the container. Based on this idea we predict that pressure will be proportional to _ _______________________________, __ ________________________________________, ______________________________________, and inversely proportional to ____________________________. Let’s derive an expression for pressure using these four variables!