1. Unit 6 Thermal Energy
8th Grade Science: KMS

2. How is Thermal Energy Transferred?
3 ways Thermal Energy can transfer:
Conduction
Convection
Radiation

3. Conduction
Conduction – the transfer of thermal energy between materials by the collisions of particles. (there needs to be direct contact of particles)
In what state of matter does conduction occur best in? Why?
Solids because the particles that make up a solid are in direct contact.

4. Conductor vs. Insulator
Conductor – material through which thermal energy flows easily. Conductors have a low specific heat
Examples: iron, aluminum, silver (best), copper, lead, brass
Insulator – a material through which thermal energy does not flow easily. Insulators have a high specific heat.
Slows the transfer of heat.
Examples: glass, wood, plastic, rubber, air, wool, cork, straw, paper.

5. Demonstrate your understanding
On the back of the Conduction sheet draw and label an example of conduction.

6. Convection
Convection – heat is transferred by the movement of currents within a fluid due to differences in density and temperature.
Convection current – The movement of a fluid, caused by differences in temperature, that transfers heat from one part of the fluid to another
This happens because hot molecules are less dense and rise whereas cold molecules are denser and sink

7. Density
Heat transfer by convection is caused by differences of temperature and density within a fluid.
Density = Mass/Volume

8. Convection heats our atmosphere

9. Convection currents also heat the Mantle

10. Demonstrate your understanding
On the back of the Convection sheet draw and label an example of convection.

11. Radiation
Radiation - The transfer of thermal energy from one material to another by electromagnetic waves.
Radiation does NOT require matter to transfer thermal energy.
All the Sun’s energy that reaches the earth travels though millions of kilometers of empty space (vacuum).
All matter can radiate energy.
You feel the radiation of thermal energy from a bonfire, a heat lamp and a light bulb through radiation.

12. Radiation
A charcoal grill radiates heat to the food you are cooking because the heat is not in direct contact with the food.

13. Radiation
For radiation to be felt as heat it must first be absorbed by a material (solid, liquid or gas)
Question: Why do blue jeans feel hotter in the sun than a yellow shirt, even though they are both exposed to the same amount of sunlight?
The blue jean fabric absorbs more radiant energy from the sun than the yellow shirt because of its dark color.

14. Conduction Radiation Convection Direct contact of particles
Occurs best in a solid
Transfer of energy by waves
Only method that can be transferred through empty space
Transfer of energy by bulk movement of matter (fluids)
Currents (wind, water)

15. Label the parts
Conduction, convection and radiation can be found in the diagram below. Label the appropriate parts.