Chemical Reactions and Energy

Question 1

What happens in exothermic reactions?

Answer 1

Energy from the reacting chemicals is transferred to the surroundings, which often increase in temperature as a result

Question 2

What happens in endothermic reactions?

Answer 2

Energy from the surroundings is transferred to the reacting chemicals, causing the temperature of the surroundings to decrease

Question 3

Which reactions are exothermic?

Answer 3

Oxidation
Neutralisation
Combustion

Question 4

Which reactions are endothermic?

Answer 4

Thermal decomposition

The reaction that happens when citric acid is combined with sodium hydrogen carbonate (sodium bicarbonate)

Question 5

How can you tell if a reaction is exothermic or endothermic?

Answer 5

By subtracting the total bond energies of the products from the total bond energies of reactants

Question 6

How would you know if a reaction is exothermic?

Answer 6

If overall energy change of reaction < 0

Question 7

How would you know if a reaction was endothermic?

Answer 7

If overall energy change of reaction > 0

Question 8

What are the energy transfers involved in bond breaking?

Answer 8

Needs heat energy. Is an endothermic process.

Question 9

What are the energy transfers involved in bond making?

Answer 9

Releases heat energy. Is an exothermic process.