Science Focus Topic 4 Notes: Expansion & Contraction | Print |
As the average energy of particles increases, the spaces between the particles increases. They expand (increase their volume) as the temperature increases. As the average energy of particles decreases, the spaces between the particles decreases. They contract (decrease their volume) as the temperature decreases.

Pure substances are matter that are made up of only one kind of particle, which can be a solid liquid or a gas.
These phases, or states have very specific properties in relation to the particle model.

 Solids Liquids Gases Shape and Size Keep their shape and size Take the shape of the container No defiinite shape or size Compressibility (volume) Cannot be compressed (fixed volume) Almost incompressible (fixed volume) Can be compressed (volume changes)

Expansion and Contraction in Solids

Solids can become longer or shorter depending on the temperature (average energy of the particles).
Table 1 (p. 211) gives precise measurements of different solid materials at different temperatures.

Expansion and Contraction in Gases

When the particles in a gas are heated, their average energy increases and they need more room, so they expand.
When the particles in a gas are cooled, the volume decreases, or contracts, because the particles need less room.

Under extremely high temperature conditions (like the temperatures inside the Sun, particles can be split into what makes them up (electrons and ions). This creates a fourth state of matter called plasma.

Expansion and Contraction in Liquids

When the particles in a liquid are heated, their average energy increases and they need more room, so they expand.
When the particles in a liquid are cooled, the volume decreases, or contracts, because the particles need less room.
This is demonstrated by the liquid used in a thermometer. As the liquid expands and contracts, it moves up and down the inside tubing ( the
bore ) of the thermometer.

Topic 4 Review p. 217