Some chemical reactions change temperature, change color, produce a gas, or make a solid from two liquids. Try this reaction and see what it does! Pour 1 tablespoon of hydrogen peroxide into a cup.

They also emit a lot of heat themselves. So how do countries keep their citizens cool and safe as heat waves become more frequent and intense without increasing their carbon footprint?

The solid-state heating and cooling process is based on transporting heat into or out of a room by loading and unloading a so-called shape memory material, for example in the form of wires.