Convection examples Which of these is an example where convection currents are created? Dark fields heating up more than green fields Sea Breeze Saucepan handle getting hot. Radiator heating a room Lesson Aims:

Convection Thinking about keeping our beaker of hot water warm for longer… What would we need to do to stop heat loss due to convection?

Lesson Aims: To answer the following questions: Why can we use Infra-Red radiation to find where people are trapped under rubble after an earthquake? Which surface is the best at emitting/ absorbing infra-red radiation?

Radiation Experiment Prediction In which thermometer will the temperature rise quickest? 1. The silver thermometer 2. The black thermometer 3. I don’t know but I would guess silver 4. I don’t know but I would guess black 5.I have no idea at all. The two thermometers are heated by the IR radiation from the lamp. One is black, one is shiny silver. Identify who already knows about radiation to challenge knowledge in experiment & who has no prior knowledge

Radiation Investigation Lesson Aims: Aim: To find out which colours absorb and emit radiation best. Diagram Observations What did you see happening? Conclusion Why did it happen? Which surfaces are best at absorbing and emitting radiation? Extension: When we come to try to keep our beaker of water warm, how would we try to prevent heat loss from radiation?

Demo Radiant Heater with different discs Lesson Aims: Radiant Heater with different discs Data logger with silver & black thermometer. Copper plate with black surface

Radiation Lesson Aims: For all transfer of heat energy there must be a difference in temperature. The energy always moves from HOT to COLD. Heat can move by travelling as infrared waves. These are electromagnetic waves, like light waves, but with a longer wavelength. This means that infrared waves act like light waves: They can travel through a vacuum. They travel at 300 000 km/s (3 x108 m/s) They can not travel through opaque materials. They can be reflected and refracted.

Finding people Lesson Aims: We can use infra-red cameras to detect people trapped under rubble after an earthquake. Use what we have learnt today to explain why… It would be hard to detect trapped bodies on a hot sunny day if the air temperature was about 35 – 40oC In order to ‘see’ the trapped person there needs to be a difference in temperature between them and their surroundings . As body temperature is 37.5oC there would be little difference in IR emitted from the body and the heated concrete.

Why does the thermal insulation for a loft often have a shiny silver surface? 1. The silver surface is good at reflecting, absorbing and emitting any Infra Red radiation. 2. The silver surface is good at reflecting and poor at absorbing or emitting the Infra red radiation. 3. The silver surface reflects the cold so keeps a house warm. 4. Answers 2 & 3 above. Make sure you understand these words: Infra Red Radiation Reflecting Absorbing Emitting 1 – incorrect, 2 – correct, 3 – have not understood radiation or Heat transfer from high heat energy to low heat energy. 4 – have understood radiation but have misconception of cold moving rather than heat energy moving from hot to cold.

Homework If you got less than 10 on banding HW: Lesson Aims: If you got less than 10 on banding HW: Conduction & convection sheet Everyone: Thermos flask sheet Due in Thursday morning please before end 1st break.