Energy Changes

Question 1

What is an endothermic reaction?

Answer 1

A reaction which takes in energy from the surroundings.

[can be shown by a fan in temperature]

Question 2

What are some examples of an endothermic reaction and its use?

Answer 2

REACTIONS ⟶ thermal decompositions.
↳ citric acid + sodium hydrogen
carbonate.
USE ⟶ some sports injury packs.

Question 3

What are some examples of an exothermic reaction and its uses?

Answer 3

REACTION ⟶ combustion.
                      ↳ neutralisation.
                      ↳ most oxidation reactions.
USES ⟶ self heating cans.
             ↳ hand warmers.

Question 4

What is an exothermic reaction?

Answer 4

A reaction which transfers energy to the surroundings.

[can be shown by a rise of temperature]

Question 5

What is the activation energy?

Answer 5

Minimum amount of energy that reactants need to react.

[be able to tell the difference between an endothermic graph and exothermic graph]

Question 6

What happens to the bonds during an endothermic reaction?

Answer 6

It is bond breaking as the energy used to break bonds is greater than the energy released by forming new bonds.

Question 7

What happens to the bonds during an exothermic reaction?

Answer 7

It is bond forming as the energy released by forming bonds is greater than the energy used to break existing bonds.

Question 8

What is the formulae to find the overall energy change?

Answer 8

Overall energy change = total energy needed to break bonds - total energy released by forming new bonds.