Explaining the Behavior of Solids
You might compare the particles in a solid to a polite audience in a movie theater. While the movie is running, people stay in their seats. Although people move around in their seats, as shown in Figure 9, each person remains in essentially the same location during the movie. They have “fixed” locations in a total volume that does not change.
Figure 9 These photographs of an audience in a movie theater were taken at different times on the same day. The behavior of the audience can be compared to the behavior of particles in a solid. Observing What stayed the same and what changed between the photographs?
Solids have a definite volume and shape because particles in a solid vibrate around fixed locations. Vibration is a repetitive back-and-forth motion. Look back at the orderly arrangement of copper atoms in Figure 2. Strong attractions among the copper atoms restrict their motion and keep each atom in a fixed location relative to its neighbors. Each atom vibrates around its location but it does not exchange places with a neighboring atom.
Section 3.1 Assessment
Reviewing Concepts
- How are shape and volume used to classify solids, liquids, and gases?
- What does the kinetic theory say about the motion of atoms?
- How is a gas able to fill a container of any size or shape?
- Use kinetic theory and attractive forces to explain why a liquid has a definite volume and a shape that can vary.
- Explain why a solid has a definite shape and volume.
How does the arrangement of atoms in most solids differ from the arrangement of atoms in a liquid?
Critical Thinking
Using Analogies Explain how the behavior of popcorn in a popcorn popper can be used as an analogy for the motion of gas particles.
Applying Concepts A hazardous chemical is leaking from a tank truck. Rescue workers need to evacuate people who live near the accident. Why are more people likely to be affected if the chemical is a gas, rather than a liquid?
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