Sodium acetate is such a useful little chemical. Not only is it responsible for the awesome flavor of salt and vinegar potato chips, but it also produces the heat in those little reusable hand and foot warmers you can buy at outdoor stores. Plus—when it's just too damn cold outside and you'd rather spend the day indoors—the same reaction that keeps your fingers and toes toasty can also be used for fun at-home art projects.
You can buy sodium acetate online, but all the real Cool Kids are making it themselves.
Maggie Koerth-Baker is the science editor at BoingBoing.net. She writes a monthly column for The New York Times Magazine and is the author of Before the Lights Go Out, a book about electricity, infrastructure, and the future of energy. You can find Maggie on Twitter and Facebook.