Foundation: 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 surroudings?
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

Describe the equipment you would use to measure the temperature change caused by an exothermic or endothermic reaction.

Answer 7

• A polystyrene cup with a lid
• In a glass beaker
• Surrounded by cotton wool
• With a thermometer in the cup

Question 8

Triple:

What are the parts of a basic electrochemical cell?

Answer 8

Two different electrodes in contact with an electrolyte (an aqueous or molten ionic compound).

Question 9

Triple:

How do electrochemical cells produce electricity?

Answer 9

Reactions between the electrodes and electrolyte set up a charge difference which makes current flow when a wire is connected to the electrodes.

Question 10

Triple:

What piece of equipment is used to measure the voltage of a cell?

Answer 10

A voltmeter.