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Unit 2: The Behavior of Atoms—Phases of Matter and the Properties of Gases


Unit Overview

Fundamentally, chemistry is the science of interacting particles. This unit covers the properties of solids, liquids, and gases in terms of the behavior of invisible particles of matter that interact at the atomic scale. Pressure, volume, temperature, and intermolecular forces are some of the variables that control these interactions and lead to the familiar macroscopic properties of matter. Developing a better understanding of the atomic model through experiments with gases, scientists discovered the Ideal Gas Law, developed phase diagrams, and learned about the properties of supercritical fluids. Today's chemists are exploring new ways to control the interactions of atoms, with the goal of making better hydrogen-powered cars and new technologies for the long-term, underground storage of carbon dioxide to reduce greenhouse warming.

by Jennifer Weeks

Jennifer Weeks


  1. Introduction
  2. Key Variables
  3. Measuring Temperature
  4. Measuring Pressure
  5. Early Gas Chemistry—Studying the Air
  6. Formulating the Gas Laws
  7. Picturing Material Behavior with Phase Diagrams
  8. Example 1—A Phase Diagram for Water
  9. Example 2—A Phase Diagram for Carbon Dioxide
  10. Conclusion
  11. Further Reading

Download Unit 2 Online Text


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