Reactions and temperature changes

Energy is transferred to or from the surroundings when a chemical reaction happens. This often causes changes in temperature that can be measured using a thermometer.

Reactions can be exothermic or endothermic. The table shows some differences.

ExothermicEndothermic
Energy Given outTaken in
TemperatureIncreasesDecreases
ExamplesCombustion, acid-alkali neutralisationElectrolysis, thermal decomposition

The slideshow describes an exothermic reaction between dilute sodium hydroxide and hydrochloric acid, and an endothermic reaction between sodium carbonate and ethanoic acid.

Sodium hydroxide solution is poured into a beaker of hydrochloric acid which contains a thermometer showing room temperature

Sodium hydroxide solution is poured into a beaker of hydrochloric acid which contains a thermometer showing room temperature

In endothermic reactions, energy enters. In exothermic reactions, energy exits.

A study of the energy changes involved in chemical reactions, whether exothermic or endothermic