Energy changes

Question 1

If a reaction releases energy to surroundings, do the products or reactants have more energy.

Answer 1

The reactants have more energy by the amount transferred.

Question 2

Define an exothermic reaction.

Answer 2

A reaction the transfers energy to the surroundings

Question 3

What type of reaction is it if after a reaction, the products have less energy?

Answer 3

Exothermic- the energy has been transferred to the surroundings.

Question 4

What type of reaction is it if after the reaction the products have more energy?

Answer 4

Endothermic- the energy has been taken in from the surroundings.

Question 5

Does the overall amount of energy change is a reaction?

Answer 5

No- energy in conserved in reactions

Question 6

List 3 exothermic reactions.

Answer 6

1. Combustion
2. Neutralisation
3. Many oxidation reactions

Question 7

List some everyday uses of exothermic reactions.

Answer 7

1. Hand warmers
2. Self-heating cans

Question 8

Define an endothermic reaction.

Answer 8

A reaction that takes in energy from the surroundings.

Question 9

List 2 endothermic reactions.

Answer 9

1. Thermal decomposition
2. Reaction between citric acid and sodium hydrocarbonate

Question 10

If the temperature of the surroundings increases what reaction is it?

Answer 10

Exothermic

Question 11

During all chemical reactions, are new bond formed or are old bonds broken?

Answer 11

Both.

Question 12

Explain in terms of bonds and energy how you know a reaction is exothermic.

Answer 12

The energy released from making bonds is greater than the energy used to break them.

Question 13

Explain in terms of bonds and energy how you know a reaction is endothermic.

Answer 13

The energy used to break bonds is greater than the energy released from making them.

Question 14

What is activation energy?

Answer 14

The minimum amount of energy required for a chemical reaction to occur.