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 ...

Cold packs come in two main types: reusable or disposable. Reusable cold pack refrigerant is usually a freezable silica gel, hydroxyethyl cellulose, or polymer. Preservatives may be used to prevent ...

Heat packs and cold packs can offer relief ... Take a bath in warm water, not hot. Don't fall asleep under a heating lamp or with a heating pad turned on -- you could burn yourself.