C5

Question 1

What is an exothermic reaction?

Answer 1

A reaction that transfers energy to the surroundings so the temperature of the surroundings increases

Question 2

Give examples of exothermic reactions

Answer 2

• combustion(fuels burnt in the presence of oxygen)
• oxidation reactions
• neutralisation

Question 3

Give everyday uses of exothermic reactions

Answer 3

• self-heating cans
• hand warmers

Question 4

What is an endothermic reaction?

Answer 4

A reaction that takes in energy from the surroundings so the temperature of the surroundings decreases

Question 5

Give examples of endothermic reactions

Answer 5

• thermal decomposition
• reaction of citric acid and sodium hydrogen carbonate

Question 6

What does a reaction profile show?

Answer 6

The relative energies of reactants and products, the activation energy and the overall energy change of a reaction

Question 7

Which is higher in an exothermic reaction profile: reactants or products?

Answer 7

Reactants

Question 8

Which is higher in an endothermic reaction profile: reactants or products?

Answer 8

Products

Question 9

When there is a positive temperature change, what type of reaction is it?

Answer 9

exothermic

Question 10

When there is a negative temperature change, what type of reaction is it?

Answer 10

Endothermic

Question 11

When there is an overall positive energy change, what type of reaction is it?

Answer 11

endothermic

Question 12

When there is an overall negative energy change, what type of reaction is it?

Answer 12

Exothermic

Question 13

What is activation energy?

Answer 13

The minimum energy needed by the particles (of the reactants) in order for them to collide for a reaction to occur

Question 14

When the chemical bonds in reactants are broken down what happens?

Answer 14

Energy is taken from the surroundings to break the bonds= endothermic

Question 15

What does ‘bond energy’ mean?

Answer 15

The amount of energy needed to break the bond between one mole of a particular covalent bond

Question 16

When the chemical bonds in the products are formed what happens?

Answer 16

energy is released when the new chemical bonds form = exothermic

Question 17

overall energy change equation?

Answer 17

energy needed to break bonds(of the reactants) - energy released when forming new bonds (of the products)

Question 18

Explain the relationship between energy needed to break bonds and energy released to form new bonds in an exothermic reaction

Answer 18

The energy released when forming new bonds is greater so there is a negative total energy change as energy is lost to the surroundings

Question 19

Explain the relationship between energy needed to break bonds and energy released to form new bonds in an endothermic reaction

Answer 19

the energy required to break bonds is greater than the energy released when forming bonds so there is positive total energy change which tells us how much more energy has been gained by the surroundings

Question 20

What is the voltage produced by a cell dependent on?

Answer 20

• type of electrode
• type of electrolyte

Question 21

How can a simple cell be made?

Answer 21

by connecting two different metals in contact with an electrolyte