Re: How many calories does drinking a gallon of 5 degree C. water burn?

Basically, your thermodynamics looks OK to me (except that for some reason you multiplied by 40 instead of 32; the number should be about 121 nutritional calories).

Your friend is right, too, BUT a gallon of water is a lot of water to drink just to use up 121 Calories (not a lot of Calories in relation to a daily intake of 2000).  Drinking a lot of water IS recommended when trying to lose weight, but that is to help fill your stomach and not for calorie loss.  For example, an article in Health pp.89-92, June 2000 says "Researchers suggest that drinking water regularly can help to reduce feelings of hunger."

David Reibstein
Outreach Director
Princeton Materials Institute