Yesterday at about 5 am I was lying in bed trying to get back to sleep when I had a great idea for a new practical. I've been trying to think of a lab that connected biology, chemistry and physics. It's for a workshop I'm running on group 4 IA later in the year. Anyway the idea was to use the heat from my hand to heat a test tube containing different amounts of water. As I lay there I thought that maybe it would take too long and there might be problems with conduction and convection in the water so wrapping a temperature probe in different amounts of Aluminium foil might be better. The aim would be to find the amount of heat given out by myhand per unit time by drawing a graph of rate of temp rise vs mass of Al. After an early breakfast I set off to the lab with my dog and tried several variations of the experiment. In my semi dream world everything worked fine but reality was different. As I added more Al foil the rate of temp rise increased.  I think this was because the area in contact with the hand got bigger. I tried with test tubes of water but got similar results, possibly also due to the more water bigger area problem. What if  just stuck one finger in a cup of water instead of holding a test tube of water? Back to the lab.