Re: Why do a batch of cookies weigh less after they are baked than the dough?

Foods of all kinds contain lots of water, and when they are cooked a lot of the water evaporates, and hence the finished product has less mass than when it started. Meats sometimes contain a lot of fat, too, so a cooked meat loses mass because of both fat and water loss. Unlike the water, though, most fat leaves the meat as a liquid, which is what you drain off when you're cooking meat.

John Link, MadSci Physicist