14.1 Gas Properties
14.1 Gas Properties
Lesson Objectives
- Describe how a gas can be compressed.
- Identify three factors that affect gas pressure. Describe the effects according to the kinetic-molecular theory.
Lesson Vocabulary
- compressibility
Check Your Understanding
Recalling Prior Knowledge
- What is the kinetic-molecular theory as it pertains to gases?
- What is responsible for a gas exerting pressure?
- How is temperature defined?
The behavior of gases is relatively easy to describe because of the large space that exists between the particles.
Because there is so much space between particles, intermolecular forces can largely be ignored, which vastly
simplifies any analysis of the motion exhibited by individual particles. In this lesson, we will begin our study of
the effect that volume, temperature, and amount has on the pressure of an enclosed gas.
Compressibility
Scuba diving is a form of underwater diving in which a diver carries his own breathing gas, usually in the form of
a tank of compressed air. The pressure in most commonly used scuba tanks ranges from 200 to 300 atmospheres.
Gases are unlike other states of matter in that a gas expands to fill the shape and volume of its container. For this
reason, gases can also be compressed so that a relatively large amount of gas can be forced into a small container.
If the air in a typical scuba tank were transferred to a container at the standard pressure of 1 atm, the volume of that
container would need to be about 2500 liters (Figure14.1).
Compressibilityis a measure of how much a given volume of matter decreases when placed under pressure. As
discussed in the chapterStates of Matter, the kinetic-molecular explains why gases are more compressible than either
liquids or solids. Gases are compressible because most of the volume of a gas is composed of the large amounts of
empty space between the gas particles. At room temperature and standard pressure, the average distance between
gas molecules is about ten times the diameter of the molecules themselves. When a gas is compressed, as when the
scuba tank is being filled, the gas particles are forced closer together.