Chemistry GCSE: C5 Energy changes

Question 1

In an endothermic reaction:

1. Do the reactants or products store more energy?
2. Is energy taken from or given to the sorroudings?
3. Does the tremperatre of the surroundings increase or decrease?

Answer 1

In an endothermic reaction:

1. The products store more energy than the reactants.
2. Energy is taken from the surroundings.
3. The temperature of the surroundings decreases: The surroundings get colder.

Endo (takes in), theramic (thermal energy).

Question 2

In an exothermic reaction:

1. Do the reactants or products store more energy?
2. Is energy taken from or given to the sorroudings?
3. Does the tremperatre of the surroundings increase or decrease?

Answer 2

In an exothermic reaction:

1. The reactants store more energy than the products.
2. Energy is given to the surroundings.
3. The temperature of the surroundings increases: The surroundings get warmer.

Exo (gives out), theramic (thermal energy).

Question 3

Give three examples of exothermic reactins

Answer 3

1. Combustion (burning).
2. Neutralisation reactions (acids +alkalis).
3. Oxidation reactions (e.g magnesium + oxygen ⇒ magnesium oxide

Question 4

A sports injury pack gets cooler without going in the freezer.

What type of reaction is this?

Answer 4

Endothermic: Energy taken in and surrounding get cooler.

Question 5

Hand warmers get warmer without heating them.

What type of reaction is this?

Answer 5

Exothermic: Energy given out, heating up the surroundings.

Question 6

Rhys buys a self heating can of hot chocolate.

What type of reaction does the can use?

Answer 6

Exothermic: Energy given out to the surrounding, heating up the hot chocolate.

Question 7

1. What is activation energy?
2. What substances change activation energy?

Answer 7

1. The amount of energy needed to start a reaction.
2. Enzymes decrease activation energy, so reactions can happen faster.