Endothermic & exothermic reactions

Energy can’t be created or destroyed only transferred

EXothermic, heat EXits, energy is transferred to the surroundings, shown by rise in temperature

• Combustion

• Neutralisation reactions

• Oxidation reactions

• Used in chemical body warmers:

  • Small metal disk placed inside pack of super saturated so,union, once you press the disk a couple times , small particles of metal are scraped off, these start off the crystallisation.

  • Crystals spread across the solution transferring heat to the surroundings in an exothermic change

ENdothermic heat ENters, energy taken from surroundings, fall in surrounding temperature

• Thermal decomposition

• Photosynthesis

• Used in chemical cold packs/ice packs

  • Ammonium nitrate and water mix to create an endothermic reaction, takes heat from surroundings making it cold.

Measuring energy transfer :

• Take a polystyrene cup and place it in a large beaker, surround the cup in cotton wool

• Keep a thermometer and stop watch ready

• Mix the reactants in the cup and place the lid on top

• As soon as the reactants are in the cup note down the starting temperature and start the stopwatch

• Note down the temperature at regular intervals until the temperature stops changing.