5. Energy changes

• exothermic reaction

  transfers energy to the surroundings, usually by heating
• how is an exothermic reaction shown?

  Rise in temperature of the surroundings
• examples of exothermic reactions

  combustion (burning)

  neutralization (acid +alkali)

  oxidation reactions
• everyday uses of exothermic reactions

  handwarmers - use exothermic oxidation of iron in air to release energy

  self heating can - exothermic reactions between chemicals in their base
• endothermic reaction

  takes in energy from the surroundings
• how is an endothermic reaction shown?

  fall in temperature
• examples of endothermic reactions

  citric acid and sodium hydrogencarbonate

  thermal decomposition
• thermal decomposition

  CaCO3 ( + heat ) -> Co2 +CaO
• what is calcium oxide also called?

  quicklime
• everyday uses of endothermic reactions

  Sports injury packs - the chemical reaction allows the pack to become instantly cooler without having to put it in the freezer.