Modelling cooling
Classroom Activity
for 11-14
What the Activity is for
In this activity, pupils build a model to explore the effects of insulation on cooling.
What to Prepare
- the modelling program VnR, installed on all computers
- a data projector connected to a computer
- sufficient computers for 2/3 pupils per computer
What Happens During this Activity
This is written as if you will talk the pupils through each step, assuming they do not have much experience with the modelling program. Start with a real cup, hot water and milk. Ask how to get the cup of tea down to just the right temperature. Steer the class towards suggesting that adding appropriate quantities of hot water and milk will get the tea to just the temperature that you want.
So then you can build the model shown.
Run the model and alter the inputs, showing how you can make the tea hot or cold by increasing or decreasing the quantities of water and milk. This is good simple science, simply represented. Allow the pupils to build this far, checking their model as they progress.
The models
Now turn attention to the fact that the tea will cool, and ask how long it will go on cooling. Build in the air temperature, and the difference between the air temperature and the tea temperature.
Pupils might build this, or you might demonstrate first before letting them have a go. Either way, ensure that at least a few pupils try running the model with the air temperature higher than the tea temperature. Ask what they expect to happen. Is the model wrong
? Now remind them that the difference in temperature between the tea and the air influences the cooling of the tea.
In fact, so long as the tea is hotter than the air, then the temperature of the tea will keep on falling. Show this feedback loop with a new kind of relationship, the grow like me
link.
Allow the pupils to explore this model, explaining to each other how it works, and following the effects of different values. Be sure to challenge each group to produce a temperature-time graph and see if they can account for its shape.
If you have any pupils who would benefit from a serious challenge, then you might ask them to alter their model to add insulation to their cup. This is tough to model, and requires that the pupils understand that the cooling effect must be divided by the extra insulation – but it's very satisfying to figure out.
