Energy Changes

Question 1

What is an exothermic reaction?

Answer 1

A reaction that releases energy to the surroundings (e.g., combustion)

Exothermic reactions often result in the release of heat or light.

Question 2

What is an endothermic reaction?

Answer 2

A reaction that absorbs energy from the surroundings (e.g., thermal decomposition)

Endothermic reactions usually result in a decrease in temperature of the surroundings.

Question 3

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

Answer 3

If more energy is released forming bonds than is absorbed breaking them, it is exothermic; otherwise, it’s endothermic

This analysis is based on the difference between total bond energies of reactants and products.

Question 4

What is activation energy?

Answer 4

The minimum energy needed for a reaction to occur

Activation energy is crucial for determining the rate of a chemical reaction.

Question 5

How do catalysts speed up chemical reactions?

Answer 5

They lower the activation energy without being used up

Catalysts provide an alternative pathway for the reaction with a lower activation energy.