Testing the effect of insulators on the rate of cooling of water: results

Material	End temperature (°C)	Drop in temperature (°C)
Polystyrene (Styrofoam)	53	12
Control	55	20
Bubble wrap	55	12
Control	53	16
Paper	50	14
Control	55	19
Foil	6	18
Control	70	17
Wet paper	40	25

Answers to questions

1. Bubble wrap and polystyrene.
2. The air trapped in the bubbles or foam is a poor conductor.
3. The wet paper towel. Water evaporates from the paper towel and cools the water down.
4. I was expecting the foil to reflect the heat energy back into the water and therefore stay warmer. It is more lightly that this is balanced against the foil conducting heat energy away from the water so there is little difference between the foil and the control results.
5. It is difficult to start both boiling tubes at exactly the same temperature. This could be solved by busing a second person to help set up the experiment of having both boiling tubes heated to the same starting temperatures by an electronic water bath. This problem is most apparent in the experiment with the polystyrene. The polystyrene container starts cooler than the control but then cools more slowly (12 °C).
6. As water evaporates it uses up heat energy from the surroundings. (The amount is described as the latent heat of vaporisation). If your body has water near it that heat energy will come from you, cooling you down.
7. As above, as the sweat evaporates from the skin the skin cools.

Credits, comments and further info

This experiment was written by staff at Sawtry College.