3-NRG-04
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Contents
Outcomes
- Pupils understand that thermal energy is transferred in three ways: conduction, convection and radiation.
- Pupils understand the process of evaporation as a decrease in thermal energy.
Specification References
4.6 recall that energy transfer may take place by conduction, convection and radiation
Starter
Popcorn example
- Popcorn can be cooked in three ways:
- By conduction in a pan with oil.
- By convection in a hot-air popper.
- By radiation in a microwave.
Main Body of Lesson
- Emphasise to pupils that "cold" doesn't move - thermal energy always moves from higher concentration (hot objects) to lower concentration (cold objects). You can draw parallels with biological examples that they may be familiar with (e.g. osmosis).
- Explain the processes of conduction, convection and radiation using heat transfers circus.
- Show pupils demonstrations of conduction, convection and radiation.
- Explain the process of evaporation as a decrease in average kinetic energy.
- Show pupils evaporation demonstration.
Practicals/Demonstrations
Conduction demonstrations
- Wood/aluminium plates (identical in appearance) with ice cubes - one melts very quickly, one very slowly.
- Rods of different metals (e.g. copper, aluminium) with embedded thermochromic thermometers (or alternatively, covered in wax) can show the progress of conduction.
Convection demonstrations
- Convection tubes; one with potassium permanganate and spirit burner; one with water and glitter.
- Smaller convection tube with can be "operated" by heat from a pupil's hand.
Radiation demonstrations
- Lesley's Cube
- Infrared thermometer
- Thermographic images
Evaporation demonstration
- Dab a small amount of alcohol from a cotton bud onto the back of pupils' hands.
Plenary
Homework
Additional Information
Resources Required
- Microwave oven
- Microwaveable popcorn
- Popping kernels
Skills Addressed
- Spear fishing
Safety/Hazards
- Flying popcorn could injure.
- Hot popcorn is hot.
- Pupil may choke on popcorn.
