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Question 1

What is an exothermic reaction?

Answer 1

A reaction that transfers heat from the chemicals to the surroundings

Question 2

What is an endothermic reaction?

Answer 2

Reactions that take in heat from the surroundings

Question 3

Examples of exothermic reactions

Answer 3

Burning fuels

Neutralisation

Question 4

Examples of endothermic reactions

Answer 4

Electrolysis
Thermal decomposition
Eating sherbet

Question 5

If you felt a container where a endothermic reaction was happening, what would you feel?

Answer 5

The surroundings and the mixture would feel colder

Question 6

If a reversible reaction is endothermic in the forward direction

Answer 6

It is exothermic in reverse

Question 7

Bond breaking is

Answer 7

Endothermic

Question 8

Bond making is

Answer 8

Exothermic

Question 9

Examples of products using exothermic reactions

Answer 9

Hand warmers

Question 10

Uses of endothermic reactions

Answer 10

Ice packs

Chill cans of drinks

Question 11

How do ice packs work?

Answer 11

It contains ammonium nitrate, which absorbs energy from its surroundings so they cool down

Question 12

How do hand warmers work?

Answer 12

Iron rusts, catalysed by salt, which provides heat

Question 13

What are the products if a reaction measured in?

Answer 13

kJ/mol

Question 14

What does the reaction profile for an exothermic reaction look like?

Answer 14

The reactants start at a higher energy level than the products as energy is released

Question 15

Why does an exothermic reaction heat up?

Answer 15

An equal amount of energy is transferred to the surroundings as is in the reaction and this energy is often heat

Question 16

What would the reaction profile for an endothermic reaction look like?

Answer 16

The reactants start at a lower level than the products because energy is absorbed from the surroundings

Question 17

What happens to the temperature of an endothermic reaction?

Answer 17

The surroundings get colder because energy is absorbed by the reaction

Question 18

What is the activation energy?

Answer 18

The minimum amount of energy needed to start a reaction

Question 19

How to see the activation energy on a reaction profile

Answer 19

The energy difference between the reactants and the peak of the curve

Question 20

What type of process is bond breaking and why

Answer 20

Endothermic, energy has to be supplied to overcome the bonds

Question 21

What type of process is bond making and whh

Answer 21

Exothermic, when bonds are formed, energy is released

Question 22

How to remember bond making and breaking process

Answer 22

Breaking bonds aBsorbs energy, foRming bonds Releases energy

Question 23

How to find how much energy is taken in or released?

Answer 23

Difference between reactants and products

Question 24

What makes a reaction exothermic in terms of bonds?

Answer 24

When the energy released when new bonds are made is more than the energy needed to break them, so it is transferred to surroundings

Question 25

What makes a reaction endothermic in terms of bonds?

Answer 25

When the energy needed to break the bonds in the reactants is more than the energy formed, so energy needs to be absorbed

Question 26

What is bond energy?

Answer 26

The energy needed to break the bond between two atoms

Question 27

How to calculate bond energies

Answer 27

1) find out how much energy is needed to break bonds in reactants 2) how much energy is released when new bonds are formed

Question 28

When a bond is broken or formed, what is the same always?

Answer 28

The amount of energy needed to make/break it

Question 29

what is the bond energy of a bond?

Answer 29

the amount of energy needed to break it

Question 30

what is it called when more energy is needed to break bonds than make bonds

Answer 30

endothermic

Question 31

what is it called when more energy is needed to make bonds than break them

Answer 31

exothermic

Question 32

what is the energy released?

Answer 32

difference between reactants and products

Question 33

how to tell what the voltage of a battery will be

Answer 33

the greater the difference in reactivity between the two elements, the higher the voltage

Question 34

when there are two metals in a cell, what happens to the electrons?

Answer 34

the most reactive donates them to the least reactive

Question 35

how does a simple cell work?

Answer 35

the more reactive metal donates electrons to the least reactive and this carries the charge

Question 36

what is a fuell cell?

Answer 36

a cell supplied by a fuel and oxygen

Question 37

how does a fuel cell work?

Answer 37

the fuel becomes oxidised and sets up a voltage

Question 38

in a fuel cell, what happens to the electrodes?

Answer 38

they switch (cathode = positive)

Question 39

in a hydrogen-oxygen fuel cell, what happens?

Answer 39

hydrogen loses electrons to produce H+ ions oxygen gains electrons to make O2 These combine to form water

Question 40

Why is hydrogen useful as a fuel?

Answer 40

When it reacts with oxygen, more energy is released in bond breaking than bond making so it is exothermic