Expansion & Contraction Chapter 8.1

Learning Outcomes: Identify examples of science & technology-based careers that are associated with heat & temperature Explain how each state of matter reacts to changes in temperature Compare, in qualitative terms, the heat capacities of some common materials

The Story So Far: All matter is made up of tiny particles. As thermal energy is added to matter, the particles move faster and spread farther apart, causing an increase in volume. On the other hand, if thermal energy is removed from matter, the particles slow down and move closer together, causing a decrease in volume.

Remember: A pure substance is a type of matter that is made of only one kind of particle. A pure substance may exist as a solid, liquid or gas on Earth. These are the three states or phases of matter.

And Now…Expansion & Contraction As materials warm up, particles move faster and spread apart. Therefore, substances will expand (increase in volume) as their temperature increases.

They will shrink or contract (decrease in volume) as their temperature decreases.

Expansion & Contraction of Solids Not all solids expand & contract the same amount when heated or cooled. The amount of thermal expansion is unique to each type of solid.

The amount of expansion of solids is very small compared with that of liquids & gases, due to the strong particle bond in solids.

Table 8.1-Stretch & Shrink Pg. 215

Expansion & Contraction of Solids Civil engineers have to think about thermal expansion & contraction when planning roadways, sidewalks, & bridges. Often they need to include expansion joints because without them, the concrete or other building material could buckle upward or outward when it expands.

Expansion & Contraction in Gases The particles in gases are farther apart than those in solids, and the forces of attraction are much weaker. Any increase in temperature causes gas particles to move quickly away from each other, so gases expand more than solids for the same temperature change.

Expansion & Contraction in Liquids Not all liquids expand the same amount when they are warmed. Liquids also do not change volume (expand or contract) in the same way.

Check Your Understanding Pg. 221 #1-5