Grade 7 Thermal Expansion & Conduction.pdf

Alberta Grade 7 Heat and Temperature
Thermal expansion and conduction.

1. Thermal Expansion &
Conduction
Or How to Get More Out of Your Atoms

2. Thermal Expansion
We know that as we add thermal energy to a substance, the component particles
begin to move with more energy. This causes both the total kinetic energy
(HEAT) as well as the average kinetic energy (TEMPERATURE) to increase.
But what are the effects of this increased kinetic energy?

3. Thermal Expansion
Well, I’m glad you asked.
Those more energetic particles begin to push each other around more, and each
particle starts to take up more room as it vibrates more. In our macroscopic
world, this means that, generally speaking, as we add thermal energy to an
object, it will begin to expand.

4. Thermal Expansion
Eventually, adding thermal energy will lead to a change of state:
Solid → Liquid → Gas
Each state of matter (for most things in the universe) takes up more space than
the previous one.

Decreasing thermal energy will have the
opposite effect, cooling a substance from
gas to liquid to solid.

5. A Demonstration of Thermal Expansion:

6. Thermal Conduction & Specific Heat
Some materials are better than others when it comes to their particles
transferring thermal energy.



Depending on the type of particles involved, heat is transferred at different rates,
and a certain amount of thermal energy will not raise the average kinetic energy
of all the particles by the same amount.

7. Thermal Conduction & Specific Heat
We refer to this quality of how much thermal energy is required to change the
temperature of a substance its Specific Heat.
Specifically, the specific heat of a material is the amount of thermal energy
needed to raise the temperature of one unit mass by 1 kelvin.
(Usually measured in joules per gram)
The smaller the specific heat, the easier it is to heat something up; that is, the
fewer joules required for each degree of temperature increase.

8. Thermal Conduction & Specific Heat

9. Predictions, please.
So, if different materials have different specific heat values, can you predict how
a strip made of two different metals sandwiched together will behave when
thermal energy is added or taken away?

10. A Demonstration of Different Thermal
Expansion due to Different Specific Heat
Values

11. Thermal Conduction
In the 5-prong Star of Death experiment, we can see the different thermal
conductive properties of different metals.

12. Convection