Commercial heat packs (containing iron and water, or supersaturated sodium acetate) and cold packs (various ammonium salts) can be used to show exo- and endothermicity. Heat packs that contain iron ...

A reusable hot pack made of a supersaturated sodium acetate solution that crystallizes spontaneously once triggered by a metal piece releases heat. A balloon filled with hydrogen gas also releases ...

A heat pack is a commercial product used by hikers and skiers as a hand warmer. It consists of a plastic pouch filled with a supercooled solution of sodium acetate (NaCOOCH 3). When a metal disc in ...

When it is exposed to air, the iron begins to rust. This rusting process produces heat. The second contains a solution of the chemical sodium acetate and a small metal disc. When the disc is bent, ...