4. Convection in a Pan - Assessment

Assessment

  1. Collect the students’ handouts and drawings.
  2. In teams, have students predict what would happen in the following scenarios.
    • You put a pot of cool water on the stove. You turn on the flame below the pot. The water at the bottom of the pot nearest the flame begins to get hot. Will convection currents be created? If so, diagram them, showing how the convection currents would move through the water. If not, explain why not.
    • You have a pot of cool water sitting on the table. You turn on a heat lamp above the pot. The water at the top of the pot nearest the heat lamp begins to get hot. Will convection currents be created? If so, diagram them, showing how the convection currents would move through the water. If not, explain why not.
    • You close all the windows and doors of the classroom. You set a portable camping stove on the floor in the middle of the room and turn the burner on. The air near the burner gets hot. Will convection currents be created? If so, diagram them, showing how the convection currents would move through the air in the room. If not, explain why not.
    • You have a rectangular pan full of water. You balance the pan on a pedestal. Under one end of the pan you light a candle. The water near that end gets hot. Under the other end of the pan you place a large pot of ice water. The water near that end gets cold. Will convection currents be created? If so, diagram them, showing how the convection currents would move through the water. If not, explain why not.
    • Think about the Pacific Ocean. The water near the equator is warmed by the sun. The water near the North and South Poles gets less direct sunlight and is very very cold. Will convection currents be created? If so, diagram them, showing how the convection currents would move through the water. If not, explain why not. (Hint, look at your answer to the previous question.)

Going Further

  1. Try the following variations:
    • Try the activity with multiple candles.
    • Sprinkle baby powder on the surface and watch the particles move.
    • Use tinfoil to shape a small, flat foil raft to represent tectonic plates. Place one or more rafts on the surface of the pan with the candle lit to model the movement of tectonic plates. (Aluminum foil works better than Styrofoam and plastic since multiple rafts will not stick to one another through static forces, and if shaped with an out-turned lip, will not stick to one another through surface tension either).
    • Once the solution is hot (has been used for 10 minutes), blow out the candle and put a piece of ice in the middle of the liquid.
    • Once the solution is hot, very carefully pick the whole pan up and set it down on a cool table.
    • Once the solution is hot, carefully slide a fifth film canister full to the brim with ice water under the pan. The surface of the ice water should contact the bottom of the pan.
    • Try the activity with a candle at one end next to a fifth film canister full to the brim with ice water a little distance away.
  2. This lesson does not discuss the relationship between temperature and volume or the concept of density. The only concept students are expected to understand is that hot things rise and that cold things sink. So study into these other concepts.
  3. Try the variation of this activity used in a UC Museum of Paleontology teacher workshop. They use a rectangular baking dish full of water with a heat source at one end and a bucket of ice water at the other.