1. The problem statement, all variables and given/known data We recently did an experiment in class and we were asked to get some ideas together to try and explain our results. We measured the time it took water to fall from 70 degrees to 65 degrees C. The water was placed in a shiny steel container (which had a volume of about 400ml). We half filled it each time and wrapped different materials around it. The first time we used no material (so just the metal can). Then we put bubble wrap around it, then black paper and finally aluminium foil. The results we found are in order of quickest to slowest fall from 70 to 65 degrees: no material, aluminium foil, black paper, bubble wrap. 2. Relevant equations None. 3. The attempt at a solution By doing some research I have some ideas. I think they all should have the same amount of convection loss from the top of the can. I think when no material was used it cooled quickest because the metal can conducted the heat to the outside of the can the quickest which meant a bigger loss from convection around the outside of the can. I'm confused about why the foil was still quick because athletes used foil blankets to reflect the infrared back to their body so shouldn't the foil wrapped around the can have worked in a similar way. Foil has a real low emissivity (0.1) so shouldn't it have retained 90% of the infrared heat from the water? I thought black had a really high emissivity which is why they use it for radiators so shouldn't it have emitted a lot of the heat away from the can?