1. 30 th April 2015 LO: To understand what affects energy transfer by radiation Radiation STARTER: If conduction and convection need particles to transfer heat energy, how does the heat energy from the Sun travel across Space to reach the Earth? https://www.youtube.com/watch?v=3DUzw6xhmBowww.youtube.com/watch?v=3DUzw6xhmBo

2. Challenge! Which will cool fastest? 1.Working with the person sitting next to you. 2.Take 4 boiling tubes. Fill each with the same volume of hot water. 3.Wrap one in black paper. One in white paper. One in silver foil. Leave one with no wrapping. 4.Record their temperatures. 5.Start timer. 6.Which do you think will lose the most heat in 10 minutes? 7.Write a prediction, explaining why you think this. 8.Record their temperatures after 10 minutes. 9.Was you prediction correct? Why?/Why not?

3. Class Results MaterialTemperature loss after 10 minutes ( ْC) 123456789101112131415Av Black paper White paper Foil No wrapping Are there any anomalous results? Can you think of any explanations for any anomalous results? Can you explain the results using the terms absorber and emitter?

4. How does this type of imaging work?

5. Call of Duty

6. Earth & The Sun The Earth is warmed by heat energy from the Sun – how does it get here?! There are no particles between the Earth and the Sun, so the heat cannot travel by conduction or convection Instead the heat travels to Earth via infrared waves – similar to light waves (with a longer wavelength), travelling at 300’000kmsec -1 (like any wave they can be reflected and absorbed)

7. Radiation In radiation, radiant energy (infra-red) is emitted by a hot object and absorbed by another cooler object. All hot objects radiate heat to the surroundings via infra-red waves – this heat radiation does not need particles, so it means heat can travel through a vacuum.

8. Radiation All objects emit (give out) some thermal radiation Some surfaces are better at emitting thermal radiation than others… Matt black surfaces are the best emitters of radiation Shiny surfaces are the worst emitters of radiation

9. What would happen if you were to repeat the experiment with cold water?

10. Radiation Infrared waves heat objects that absorb (take in) them Some surfaces are better at absorbing thermal radiation than others – good emitters are also good absorbers Matt black surfaces are the best absorbers of radiation Shiny surfaces are the worst absorbers because they reflect most of the radiation away

11. Leslie Cube A Leslie cube is a device that has sides made from different materials. It is filled with hot water and the energy emitted from each side is measured. Can you explain which side will record the highest temperature? Use the terms absorber and emitter.

12. Homework ( write this in your planner) Due in on Thursday 7 th May Explain the three methods of heat transfer

13. Quiz