Exothermic reactions are accompanied by a temperature rise. They transfer heat energy to the surroundings, i.e they give out heat.
Common examples of exothermic reactions include:
- neutralising alkalis with acids
- self-heating can
Enothermic reactions are accompanied by a fall in temperature. Heat energy is transferred from the surroundings, i.e they take heat in.
Thermal decompostition and dissolving ammonium nitrate crystals in water are example of endothermic reactions.
If a reversible reaction is exothermic in one direction then it is endothermic in the opposite direction. The same amount of energy is transferred in each case.<- The symbol for a reversible reaction