topic 5

Question 1

what happens during a chemical reaction?

Answer 1

old bonds are broken and new bonds are formed

Question 2

what is supplied to break existing bonds?

Answer 2

energy

Question 3

what process is bond breaking?

Answer 3

an endothermic process

Question 4

when new bonds are formed…

Answer 4

energy is released

Question 5

what process is when engergy is released?

Answer 5

exothermic

Question 6

what process is bond formation?

Answer 6

exothermic process

Question 7

An exothermic reaction is…

Answer 7

when energy is given out

Question 8

what must always be supplied to break bonds?

Answer 8

energy

Question 9

what reaction is it when the heat energy released is greater than the energy used in breaking bonds?

Answer 9

exothermic reaction

Question 10

give an example of an exothermic reaction

Answer 10

burning fuels - making new bonds in the product gives out more heat energy than it takes to break the bonds in the fuel

Question 11

an endothermic reaction is…

Answer 11

when energy is taken in

Question 12

what happens in an endothermic reaction?

Answer 12

the energy needed to break old bonds in the reactants is more than the heat energy released when new bonds are formed in the products

Question 13

what is an example of an endothermic reaction?

Answer 13

photosynthesis uses light energy from the sun to convert carbon dioxide and water into glucose and oxygen

Question 14

what process is more common? endothermic or exothermic?

Answer 14

exothermic

Question 15

describe an exothermic graph

Answer 15

the products are at a lower energy than the reactants

Question 16

describe an endothermic graph

Answer 16

the products are at a higher energy than the reactants

Question 17

on a exothermic reaction what does the initial line represent?

Answer 17

the energy needed to break the bonds

Question 18

on an endothermic graph what does the difference in height represent?

Answer 18

the energy that is taken I’d during the reaction

Question 19

what do energy level diagrams show?

Answer 19

whether it’s an endothermic reaction or an exothermic reaction

Question 20

give and example of a slow reaction

Answer 20

rusting of iron

Question 21

give an example of a moderate speed reaction

Answer 21

a metal (like magnesium) reaction with acid - produces a gentle stream of bubbles

Question 22

give an example of a really fast reaction

Answer 22

an explosion - it’s all over in a fraction of a second

Question 23

what are the four things that the rate of a reaction depends on?

Answer 23

temperature
concentration (pressure for a gas)
catalyst
surface area (or size of particles)

Question 24

how do you increase the surface area of a solid?

Answer 24

crush the solid up into smaller pieces

Question 25

why does the retraction speed up if you have a larger surface area?

Answer 25

there are more pieces of the solid so there are more collisions which produces more energy to speed up the reaction

Question 26

describe how to conduct an experiment to measure the rate of a reaction (hydrochloric acid and marble chips)

Answer 26

- using a syringe measure the amount of gas and do it at different time intervals - make a table of readings and plot a graph - repeat the same steps as before but crush the marbles chips into smaller pieces so that they have a larger surface area - then repeat th experiment again with the same mass of powdered marble chips rather than marble chips

Question 27

more gas is enclosed when there's a ...

Answer 27

quicker reaction

Question 28

when looking at the effects that using more concentration has on the rate of a reaction is there a steeper graph when the concentration is higher or lower?

Answer 28

higher - quicker reaction

Question 29

what does a catalyst do?

Answer 29

speed up a reaction

Question 30

what is a catalyst?

Answer 30

a substance which changes he speed of a reaction but is not being used up in the reaction

Question 31

how does a catalyst work?

Answer 31

lowers the amount of energy that is required by the reactants to react

Question 32

because a catalyst lowers the energy required by the reactants to react why does it make it easier for the reaction to happen?

Answer 32

a lower temperature can be used without the rate of the reaction decreasing

Question 33

where are catalytic converters founds?

Answer 33

motor vehicles - vehicle exhausts

Question 34

why do vehicle exhausts use catalytic converters?

Answer 34

they can give of poisonous gases like carbon monoxide if petrol doesn't burn properly

Question 35

what does a catalytic converter do?

Answer 35

increases the rate at which carbon monoxide and in burnt fuel in exhaust gases react with oxygen in the air to produce carbon dioxide and water

Question 36

when does a catalyst work best in a catalytic converter?

Answer 36

when it has a large surface area and it has a high temperature to increase the rate of the reaction

Question 37

more collisions increase the rate of reaction. true or false?

Answer 37

true

Question 38

how does a higher temperature increase collisions?

Answer 38

the particles move quicker so they have more frequent collisions

Question 39

how does a higher concentration (pressure) increase the amount of collisions?

Answer 39

concentration: if a solution is made more concentrated there are more particles of reactant moving between the water molecules so it makes the collisions more likely pressure: the particles are more quashed up meaning they are going to be more frequent collisions

Question 40

how does a larger surface area effect the amount of collisions?

Answer 40

breaking a solid up into smaller pieces means that there will be more pieces in the solution so there will be a larger surface area to react with meaning there will be more frequent collisions

Question 41

how does a catalyst increase the number of SUCCESSFUL collisions?

Answer 41

it gives the reacting particles a surface to stick to so the energy that particles needs to react is lowered

Question 42

slower collisions increase the rate of reaction. true or false?

Answer 42

false - faster collisions increases the rate of reaction

Question 43

how are faster collisions increases?

Answer 43

ONLY by temperature

Question 44

reactions can only happen if...

Answer 44

there is enough energy when the particles collide because a minimum amount of energy is needed to break the initial bond

Question 45

covalent substances are one ...

Answer 45

non-metal and one metal