# 8: Gases

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In this chapter, we 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.

Unit 8 Objectives

By the end of this unit, you will be able to:

• Define pressure and atmospheric pressure.
• List atmospheric pressure at sea level in atm, mmHg, Torr, Psi, kPa, bar, and millibar and perform atmospheric pressure unit conversions.
• Identify the mathematical relationships between the various properties of gases.
• Describe the major gas laws including Boyle’s Law, Amanoton’s Law, Charles’ Law, the Combined Gas Law, and the Ideal Gas Law, and properly use the formulas associated with these laws.

• 8.1: Gas Pressure
Gases exert pressure, which is force per unit area. The pressure of a gas may be expressed in the SI unit of pascal or kilopascal, as well as in many other units including torr, atmosphere, and bar. Atmospheric pressure is measured using a barometer; other gas pressures can be measured using one of several types of manometers.
• 8.2: Relating Pressure, Volume, Amount, and Temperature- The Ideal Gas Law
The behavior of gases can be described by several laws based on experimental observations of their properties. including Amontons’s law, Charles’s law, Boyle’s lawand Avogadro’s law. These laws can be extracted directly from the ideal gas law.
• 8.3: The Kinetic-Molecular Theory
The kinetic molecular theory is a simple but very effective model that effectively explains ideal gas behavior. The theory assumes that gases consist of widely separated molecules of negligible volume that are in constant motion, colliding elastically with one another and the walls of their container with average velocities determined by their absolute temperatures. The individual molecules of a gas exhibit a range of velocities.
• 8.4: Unit 8 Practice Problems

## Contributors

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