Science Buddies: "Ask an Expert"

Hi - we did an experiment burning willow chips under a beaker of water - taking the temperature difference of water before and after - and change of mass of willow chip during combustion. My results are slightly different than I was hoping for. I wanted to just show as mass increased, energy content increased. The chipping that was the lightest at beginning actually had the most heat quantity (Q= mass of water x specific heat capacity of water x change in temp of water) - also it was the wood chip that lost the least amount of mass only .28 g (the others were close to .5g), so can I explain this by saying that it has less water content at beginning so that was probably why it didnt' lose so much mass and why its energy output was so much greater.

Thanks for help.

No, thats not quite the way it works. Because of the fact that We know that Density = Mass / Volume, the explanation would be useless, unless you could show that the lighter mass had a difference in density from the higher mass. Such difference would indicate greater dehydration of the product, thus making it more likely to burn effectively. What you're really after here is measuring specific gravity, which is a ratio of Density as compared with the Density of Water. The more dehydrated a substance is, the greater the Specific Gravity.