Energy Conservation
Chemistry: Edexcel IGCSE, topic 14.1.1
Energy Transfer/Conservation
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 that happens when citric acid is combined with sodium hydrogen carbonate (sodium bicarbonate).
Test yourself on Energy Conservation
Why does the temperature of the surroundings often increase during an exothermic reaction?