Exo/Endothermic reactions and Bond energies

Exothermic reaction

A reaction that releases energy to surroundings

Example of an exothermic reaction

Combustion

Endothermic reaction

A reaction that takes in energy from its surroundings

Example of an endothermic reaction

Melting with a Bunsen burner

Activation energy

The minimum amount of energy the reactant particles need to collide with each other and react

What type of reaction is this?

Endothermic reaction

What type of reaction is this?

Exothermic reaction

Label A

Reactants

Label B

Activation energy

Label C

Products

Label D

Overall change in energy

Bond energies definition

the amount of energy required to break one mole of a particular covalent bond

How much 1 mole is

Avogadro’s constant: 6.02×10²³

What bond breaking is in terms of energy

It is an endothermic process

What bond making is in terms of energy

It is an exothermic process

How to determine whether a reaction is exothermic or endothermic

Compare the total amount of energy released when the bonds form, to the total amount of energy required to break the bonds

How to calculate the overall energy change of a reaction

energy required to break bonds (reactants) - energy released by forming bonds (products)

What a negative energy change means

That it has lost energy so the reaction is exothermic

What does a positive energy change mean

It had gained energy, so the reaction is endothermic