Unit 5 - Chemical energetics Flashcards
Exothermic reaction
A reaction that gives out energy into the surroundings creating a temperature increase
Endothermic reaction
A reaction that takes in energy from the surroundings causing a temperature decrease
Examples of exothermic reactions
- Freezing water
- Combustion
- neutralization reactions
- Metal displacement reactions
- Respiration
Examples of endothermic reactions
- Electrolysis
- Melting of ice
- Thermal decomposition
- Cracking
- Photosynthesis
Activation energy
The minimum amount of energy that particles need to have when they collide if they are going to react
Enthalpy change
The overall energy change of a reaction
Unit of enthalpy change
kJ/mol
Bond energy in exothermic reactions
The energy released when bond making is greater than the energy required to form new bonds - the surplus energy is released
Bond energy in endothermic reactions
The energy need to break bonds is greater than the energy released when new bonds form - energy must be absorbed
