Cold weather makes for cold hands—unless, of course, you have a hand warmer. Don't waste money on those cheap disposable ones. Instead, use kitchen chemistry to make your own reusable versions.

When vinegar and baking soda react, they form a compound called sodium acetate. This chemical has a high freezing point, so in liquid form at room temperature, it is supercooled. In such a state, a single sodium acetate crystal will trigger all the liquid to freeze solid, which releases enough energy to heat a bag of sodium acetate to about 136°F. Once it cools down, users can drop the bag into boiling water, reliquefying the chemical and readying it for another use.

To make a portable hand warmer, seal some sodium acetate, an alligator clip, and a crystal in a vinyl packet. When the chemical solidifies, squeezing the clip open and closed will trap crystals between its teeth. Heat the packet to liquefy the contents, and when you're ready for instant warmth, pinch the clip to expose the crystals.