- Created by: holly6901
- Created on: 04-04-19 16:41
Energy from the surroundings is transferred to the reacting chemicals, causing the temperature of the surroundings to decrease. Examples include:
- Thermal decomposition.
- The reaction between citric acid and sodium hydrogen carbonate (sodium bicarbonate).
Energy from the reacting chemicals is transferred to the surroundings, which often increase in temperature as a result. Examples include:
In exothermic reactions, energy from the reacting chemicals is transferred to the surroundings. This often leads to an increase in temperature. Examples include:
- Hand warmers
- Disposable hand warmers use the energy released by iron oxidation.
- Reusable hand warmers source their energy from the crystallisation of salt solutions. Boiling the pack re-dissolves the crystals, so that it's ready to be activated once more.
In endothermic reactions, energy from the surroundings is transferred to the reacting chemicals. This decreases the temperature of the surroundings. Examples include:
- Sports injury packs
- When squeezed forcefully, ammonium nitrate and water mix in the pack, resulting in instant cooling.
- The speed of this reaction makes these packs ideal for scenarios when ice is not immediately available.
- Thermal decomposition
- Citric acid and baking soda
Requirements for a reaction
There are 2 main requirements for a successful reaction to take place:
- Reacting particles must collide.
- Activation energy
- Collisions must take place with sufficient energy (the activation energy).
Reaction profiles show the progress of reaction on the x axis and energy level on the y axis. They contain the following information:
- The relative energies of reactants and products.
- The activation energy of a reaction.
- The overall energy change of a reaction.
Catalysts can increase reaction rates by lowering the activation energy, which increases the likelihood of successful collisions.