Behavior of a Gas

Introduction

We think of a gas as a collection of tiny particles in random, thermal motion. When they collide with the sides of a container, they exert a force on the container walls. The average force resulting from these collisions on each unit area of the container is called the pressure exerted by the gas. You are familiar with everyday units of pressure, such as psi (pounds per square inch) to describe tire pressure or inches of mercury to describe atmospheric pressure. For this experiment, we will use the SI unit of pressure, the pascal, which is defined as one Newton of force acting on each square meter of surface. Since the Newton is smaller than a pound and a square meter is much larger than a square inch, we will use kilopascals, kPa, to describe the pressure of a gas.

You will certainly recognize what variables might affect the pressure of a gas in a container. In this experiment, you will develop quantitative relationships between pressure and these variables.

Objectives

In this experiment, you will

• Collect pressure vs. volume, pressure vs. number, and pressure vs. temperature data for a sample of air in an enclosed container.
• Determine relationships between these pairs of variables.
• Determine a single expression relating these variables.
• Determine the constant of proportionality for the relationship between pressure, volume, and temperature.
• Use kinetic molecular theory (KMT) to model the behavior of the gas at various points on each graph.