1. Thermal Expansion Magnitude of Expansion of Solids, Liquids and Gases
Examples of Expansion
Relationship between pressure and volume at a constant temperature

2. Thermal Expansion
When molecules are heated they move far apart from each other
This causes the material to expand
Expansion
Increase in size of a material due to added heat
When molecules are cooled, the molecules, move closer to each other
This causes the material to contract
Contraction
Decrease in size of a material due to heat removed

3. Let us look at 3 videos on the example of expansion and contraction

4. Applications of Thermal Expansion
Bimetallic strip as thermometer

5. Applications of Thermal Expansion
Road expansion gaps
Liquid Expansion as thermometer

6. Applications of Thermal Expansion
Tyre Fitting

7. Thermal Expansion All materials expand
Solids have linear expansion
Varies among materials
Liquids and Gases have volume expansion
Gases expands more readily than gas
When a materials changes from solid to liquid, volume does not change much
When a liquid changes to gas, the volume expansion is about 1000 times more

8. Pressure of a Gas Pressure of a gas Force per unit area
Force is due to collisions with the walls of the container
Units: Nm-2 or pascal, Pa

9. Pressure and Volume of a Gas at Constant Temperature
At constant temperature, what happens to the volume of the gas when the pressure increases?
At constant temperature, what happens to the pressure of the gas when the volume decreases?
Boyle’s Law
Pα1/V
pV = constant
p1V1=p2V2