C3.2 Energetics

Question 1

Define exothermic reaction

Answer 1

• Reaction that releases energy into surroundings

- Increases temperature of reaction mixture

Question 2

Give 2 examples of exothermic reactions

Answer 2

• Combustion

- Neutralisation

Question 3

Define endothermic reaction

Answer 3

• Reaction that absorbs energy from surroundings

- Decreases temperature of reaction mixture

Question 4

Give 2 examples of endothermic reactions

Answer 4

• Reaction between citric acid and sodium hydrogen carbonate

- Photosynthesis

Question 5

Define activation energy

Answer 5

Minimum energy needed for a reaction to start

Question 6

What are bond energies measured in?

Answer 6

Kilojoules per mole (kJ/mol)

Question 7

What two things do you need to consider when using bond energies to calculate energy changes in reactions?

Answer 7

• Energy transferred to break the bonds in the reactants

- Energy transferred when bonds form in products