Energy Changes

Question 1

What are some examples of exothermic reactions?

Answer 1

Neutralisation
Combustion
Oxidation

Question 2

What are some examples of endothermic reactions?

Answer 2

Cracking
Photosynthesis
Electrolysis

Question 3

Describe an exothermic energy diagram.

Answer 3

The reactants have more energy than the products. As a result this energy would be released to the surroundings causing the temperature to rise.

Check notes. Ea higher than ΔH
-KJ

Question 4

Describe an endothermic energy diagram.

Answer 4

The reactants have less energy than the products. As a result this energy is taken in from the surroundings causing the temperature to decrease

Check notes. Ea less than ΔH
+KJ

Question 5

What is the Activation energy?

Answer 5

The minimum amount of energy required for a reaction to take place.

Question 6

How can the overall energy change of a reaction be calculated?

Answer 6

Energy put in (endo) to break the bonds (reactants) - energy released (Exo) when new bonds are formed (products)

Question 7

What is bond energy?

Answer 7

The amount of energy required to break one mole of a specific covalent bonds.

These are given in a table in energy change questions. Use these to calculate the overall energy used in reactants and released in products and take them away to find the energy change.