ChemistryCode 5070
Exothermic and endothermic reactions
What this topic asks you to be able to do
- State that an exothermic reaction gives thermal energy out to its surroundings, so that the temperature of those surroundings rises
- State that an endothermic reaction absorbs thermal energy from its surroundings, which causes the temperature of those surroundings to fall
- State that the thermal energy transferred during a reaction is known as its enthalpy change, ΔH, and that ΔH has a negative value for exothermic reactions and a positive value for endothermic ones
- Define activation energy, Ea, to be the smallest amount of energy that particles need when they collide in order to react
- Draw, label and interpret, from the information supplied, reaction pathway diagrams for exothermic reactions and for endothermic reactions, showing: (a) reactants (b) products (c) the reaction's enthalpy change, ΔH (d) activation energy, Ea
- State that bond breaking counts as an endothermic process and bond making as an exothermic one, and account for how a reaction's enthalpy change arises from bond breaking and bond making
- Work out a reaction's enthalpy change from bond energies