What the activity is for
In this activity, pupils will explore the effects of insulation on cooling.
What to prepare
- 35 millimetre film canisters, drilled through the lid to accept a temperature probe
- a temperature probe plus data logger
- rectangular strips of fleece material, cut to fit around the perimeter of the canister. The strips are all cut to the same height, but of 5 different lengths, to fit around the canister one, two, three, four or five times
- expanded polystyrene lid to prevent significant cooling through the top of the canister
- expanded polystyrene base to prevent significant cooling through the bottom of the canister
- kettles and a supply of water
What happens during this activity
Get the pupils to think about the effect of adding extra layers of insulation on cooling, perhaps drawing on the activity
Show the cooling curve from an un-insulated canister, and get small groups to predict the effect on the curve of adding successive layers of insulation. Record their predictions, perhaps as a series of sketch graphs. Then, if possible, get the pupils to carry out the experiment themselves, recording their results.
Having plenty of apparatus allows the pupils to explore the effects of one, three and five, or none, two and four thicknesses all at once (many data capture devices only have three temperature probes, so this is the principal limitation). The pupils should compare their predictions to the results.
It is important to draw attention to the diminishing returns which are apparent here, as the extra layers are added. Thus adding layer five makes less difference than adding layer two, all layers being of equal thickness. Each layer reduces power by a constant fraction (reducing an effect by a constant fraction is such an important pattern in nature that you might want to draw attention to it here).