Topic C5 - Endothermic & Exothermic Reactions

Question 1

What is an endothermic reaction

Answer 1

Takes in energy from surroundings
Shown by a fall in temperature

Question 2

What is an exothermic reaction?

Answer 2

Transfers energy to the surroundings
Shown by a rise in temperature

Question 3

Examples of endothermic reactions

Answer 3

Thermal decompositions
Citric acid + sodium hydrocarbonate

Question 4

Examples of exothermic reactions

Answer 4

Combustion
Neutralisation
Most oxidation reactions

Question 5

What is activation energy?

Answer 5

Minimum amount of energy that reactants need to react

Question 6

What reaction is bond breaking

Answer 6

Endothermic - energy used to break bonds is greater than the energy released by forming new bonds

Question 7

What reaction is bond forming

Answer 7

Exothermic - energy released by forming bonds is greater than the energy used to break existing bonds

Question 8

How to calculate overall energy change?

Answer 8

Overall energy change = total energy need to break bonds — total energy released by forming new bonds