Exothermic & Endothermic Reactions

In chemical reactions, energy is not created or destroyed. It is conserved (saved) and transferred between objects. Chemical reactions are exothermic or endothermic, depending on the energy transfers that happen.

Exothermic reactions

Energy from the reacting chemicals is transferred to the surroundings, which often increase in temperature as a result. Examples include:

  • Combustion
  • Neutralisation
  • Oxidation

Endothermic reactions

Energy from the surroundings is transferred to the reacting chemicals, causing the temperature of the surroundings to decrease. Examples include:

  • Thermal decomposition
  • The reaction between citric acid and sodium hydrogen carbonate (sodium bicarbonate).

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