C5

Question 1

Define exothermic reaction

Answer 1

Transfer energy from the reacting molecules to the surroudings - temperature of the surroundings increase.

Question 2

3 examples of exothermic reactions

Answer 2

Combustion (burning), certain oxidation reactions, neutralisation

Question 3

2 uses of exothermic reactions

Answer 3

Hand warmers, self-heating cans for food and drink

Question 4

Define endothermic reaction

Answer 4

Take in energy from their surroundings - temperature of surroundings decrease.

Question 5

Example of an endothermic reaction

Answer 5

Thermal decomposition

Question 6

Define activation energy

Answer 6

The minimum amount of energy that particles must have in order to react.

Question 7

Are exothermic energy changes positive or negative?

Answer 7

Negative

Question 8

Are endothermic energy changes positive or negative?

Answer 8

Positive

Question 9

How to break a chemical bond?

Answer 9

Use energy (endothermic)

Question 10

How to make a chemical bond?

Answer 10

Release energy (exothermic)

Question 11

Define independent variable

Answer 11

One which we change.

Question 12

Define dependent variable

Answer 12

One which changes because we change the independent variable.

Question 13

Define control variable

Answer 13

Variable that is kept the same during the experiment.

Question 14

Why is a polystyrene cup used?

Answer 14

It is a good thermal insulator so reduces heat loss.