Saturday, July 09, 2005

Self heating coffee

As covered on Slashdot, here's a guy who took apart a self-heating coffee product to see how it works.

Interestingly, the source of heat comes from Calcium Oxide, which is also known as Quicklime. Basically, if you take some calcite limestone (Calcium Carbonate, that's the bedrock where I live) and heat it for a long time, it turns into Quicklime (and in the process, releases Carbon Dioxide). Add water to Quicklime, and I *think* that it turns into hydrated lime (Calcium Hydroxide?), but in the process, gets very hot.

The self heating coffee apparently has about 8oz of Quicklime powder packed into a chamber of the cup itself, and when activated, water is introduced into the Calcium Oxide, creating the chemical reaction.

In high school Chemistry class, we made Quicklime, and our teacher then instructed us to hold a small piece on our hand and add one drop of water. We learned "first hand" what an exothermic reaction was!