Exothermic reactions

An exothermic reaction is a reaction where the substances react chemically to release energy in the form of heat.

An example of this is combustion (burning). Exothermic reactions transfer energy to the surroundings. The energy is usually transferred as heat energy, causing the reaction mixture and its surroundings to become hotter. The temperature increase can be detected using a thermometer. Some examples of exothermic reactions are:

• burning
• neutralisation reactions between acids and alkalis
• the reaction between water and calcium oxide

The chemical reaction that does the complete opposite, and absorbs heat, is an endothermic reaction.

Exothermic Reactions Media

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  Explosions are some of the most violent exothermic reactions.

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  An exothermic thermite reaction using iron(III) oxide. The sparks flying outwards are globules of molten iron trailing smoke in their wake.