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Hand warmers are small (sometimes disposable) packets which are held in the hand and produce heat on demand to warm cold hands. Wikipedia does not have an article with this exact name. ... A heating pad is a pad used for warming of parts of the body in order to manage pain. ... A red-hot iron rod cooling after being worked by a blacksmith. ...

They are commonly used in outdoor activities such as hiking and skiing to keep the extremities warm and assist insulated clothing. Other types of warmers are available to provide soothing heat for muscular or joint aches.

Some hand warmers contain cellulose, iron, water, activated carbon, vermiculite and salt and produce heat from the exothermic oxidisation of iron when exposed to air. Cellulose (C6H10O5)n is a long-chain polymer polysaccharide carbohydrate, of beta-glucose. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ... Activated carbon (also called activated charcoal) is the more general term which includes carbon material mostly derived from charcoal. ... Vermiculite is a natural mineral which expands with the application of heat. ... A magnified crystal of salt In chemistry, salt is a term used for ionic compounds composed of positively charged cations and negatively charged anions, so that the product is neutral and without a net charge. ... Exothermic has several meanings, including: In biology, an exothermic or poikilothermic animal is one that requires external sources of heat (usually sunlight) to maintain its internal temperature: for example, reptiles. ... Air is a name for the mixture of gases present in the Earths atmosphere. ...

A second type generate heat through exothermic crystallisation of supercooled molten materials (usually sodium acetate) and are reusable. These can be recharged by boiling the warmers and allowing them to cool. Heating of the pads is triggered by snapping a small metal device buried in the pad which generates shock waves to initiate crystallisation. Quartz crystal A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ... Supercooling is the process of chilling a liquid below its freezing point, without it becoming solid. ... In fluid dynamics, a shock wave is a nonlinear or discontinuous pressure wave. ...

A third type uses lighter fluid (lighter fuel) or LPG which is reacted with a platinum catalyst to release heat by oxidation reactions. These can be used on many occasions by simply refuelling. A metal naphtha lighter A lighter is a device used to create fire with the intent to ignite another substance such as a cigarette, smoking pipe, bong, hookah or charcoal in a grill. ... Liquified petroleum gas (also called liquefied petroleum gas, liquid petroleum gas, LPG, LP Gas, or autogas) is a mixture of hydrocarbon gases used as a fuel in heating appliances and vehicles, and increasingly replacing fluorocarbons as an aerosol propellant and a refrigerant to reduce damage to the ozone layer. ... General Name, Symbol, Number platinum, Pt, 78 Chemical series transition metals Group, Period, Block 10, 6, d Appearance grayish white Atomic mass 195. ...

Depending on the type and the source of heat, hand warmers last between 30 minutes (recrystallisation) though to 12 - 24 hours.

External links

• ScienceIQ.com - Hand warmers