Energy Change

Exothermic reactions:

  • Transfer of energy from reacting chemicals to the surroundings.

  • Increases in temperature


Example:

  • Combustion

  • Respiration

  • Neutralisation

  • Also Hand warmers and self-heating cans


Endothermic energy:

  • Involve transfer from the surroundings to the reacting chemicals

  • Would decrease in temperature


Example:

  • Thermal decomposition of calcium carbonate

  • Eating sherbet

  • Instant ice packs



Activation Energy - the minimum amount of energy is required for a chemical reaction to take place.

Catalysts - increase the rate of a reaction. Catalysts provide an alternative pathway for a chemical reaction to take place by lowering the activation energy.


Practical:

  1. Gather the equipment

  2. Place the polystyrene cup inside the beaker (prevent cup from falling over)

  3. Using measuring cylinder, measure out 30cm (cubed) of the acid. Such as hydrochloric or sulfuric acid may be used. Pour into the polystyrene cup.

  4. Using top pan balance, measure appropriate amount of the solid (for example: 10g) or use one strip of a metal such as magnesium.

  5. Add solid to the acid and record temperature.