ENERGY CHANGES

Question 1

What is an exothermic reaction?

Answer 1

Energy transfer to the surroundings.

Question 2

What is an endothermic reaction?

Answer 2

Energy transfer from the surroundings to an object.

Question 3

What happens to the temperature in an exothermic reaction?

Answer 3

The temperature increases.

Question 4

What happens to the temperature in an endothermic reaction?

Answer 4

It decreases.

Question 5

Compare the products and reactants in an exothermic reaction?

Answer 5

The products have less energy than the reactants in an exothermic reaction.

Question 6

Compare the reactants and products in an endothermic reaction?

Answer 6

The products have more energy than the reactants in an endothermic reaction.

Question 7

What does an acid and an alkali give you?

Answer 7

Salt and water.

Question 8

What does nitric acid and potassium hydroxide give you?

Answer 8

Potassium nitrate and water.

Question 9

What does lithium hydroxide and sulphuric acid acid give you?

Answer 9

Lithium sulphate and water.

Question 10

What ions does an acid release?

Answer 10

Hydrogen ions (H+).

Question 11

What ions do Alkalis release?

Answer 11

Hydroxide ions (OH-).

Question 12

Uses of neutralisation?

Answer 12

Indigestion remedied.

Neutralise acidic soil - use calcium hydroxide.

Question 13

What solid is used in self heating cans?

Answer 13

Calcium

Calcium oxide + water ——> calcium hydroxide.

Question 14

What is activation energy?

Answer 14

The minimum amount of energy needed before colliding particles of reactants have sufficient energy to cause a reaction. What

Question 15

What is the energy change in an exothermic reaction?

Answer 15

Chemical -> heat

Question 16

What is the energy change in an endothermic reaction?

Answer 16

Heat -> chemical

Question 17

Give examples of where exothermic reactions can be used usefully?

Answer 17

Hand and body warmers.

Self-heating cans

Question 18

Give examples of where endothermic reactions can be used usefully?

Answer 18

Chemical cold packs.

Chilling cans of drink.

Question 19

What process in bond breaking?

Answer 19

Endothermic - energy has to be supplied to break chemical bonds therefore energy is taken from the surroundings.

Question 20

What process in bond making?

Answer 20

Exothermic.

Question 21

If more energy is released when breaking the bonds in the reactants than when making the new bonds formed in the products what type of reaction is it?

Answer 21

Endothermic.

Question 22

If more energy is released when making the new bonds than when breaking the bonds in the reactants what type of reaction is it?

Answer 22

Exothermic.

Question 23

What does the voltage tell you about the reactivity of a metal?

Answer 23

The greater the difference in reactivity between the two metals used, the higher the voltage produced.

Question 24

How is a simple electrical cell created?

Answer 24

When two metals are dipped in a salt solution and joined by a wire, the more reactive metal will donate electrons to the less reactive metal.

Question 25

Advantages of hydrogen fuel cells?

Answer 25

Do not need to be electrically recharges.
No pollutants are produced
Can be a range of sizes for different users.

Question 26

Disadvantages of hydrogen fuel cells?

Answer 26

Hydrogen is highly flammable
Hydrogen is sometimes produced for the cell by non-renewable sources.
Hydrogen is difficult to store.

Question 27

Talk about how hydrogen fuel cells work.

Answer 27

The cells are fed with hydrogen and oxygen and produce water. Hydrogen gas is supplied as a fuel to the negative electrode. It diffuser through the graphite electrode and reacted with hydroxide ions to form water and provided a source of electrons to an external circuit.
Oxygen gas is supplied to the positive electrode. It diffuser through the graphite and reacts to form hydroxide ions, accepting electrons from the external circuit.