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additional chemistry > topic 5 > Flashcards

topic 5 Flashcards

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1
Q

what happens during a chemical reaction?

A

old bonds are broken and new bonds are formed

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2
Q

what is supplied to break existing bonds?

A

energy

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3
Q

what process is bond breaking?

A

an endothermic process

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4
Q

when new bonds are formed…

A

energy is released

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5
Q

what process is when engergy is released?

A

exothermic

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6
Q

what process is bond formation?

A

exothermic process

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7
Q

An exothermic reaction is…

A

when energy is given out

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8
Q

what must always be supplied to break bonds?

A

energy

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9
Q

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

A

exothermic reaction

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10
Q

give an example of an exothermic reaction

A

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

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11
Q

an endothermic reaction is…

A

when energy is taken in

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12
Q

what happens in an endothermic reaction?

A

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

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13
Q

what is an example of an endothermic reaction?

A

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

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14
Q

what process is more common? endothermic or exothermic?

A

exothermic

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15
Q

describe an exothermic graph

A

the products are at a lower energy than the reactants

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16
Q

describe an endothermic graph

A

the products are at a higher energy than the reactants

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17
Q

on a exothermic reaction what does the initial line represent?

A

the energy needed to break the bonds

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18
Q

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

A

the energy that is taken I’d during the reaction

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19
Q

what do energy level diagrams show?

A

whether it’s an endothermic reaction or an exothermic reaction

20
Q

give and example of a slow reaction

A

rusting of iron

21
Q

give an example of a moderate speed reaction

A

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

22
Q

give an example of a really fast reaction

A

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

23
Q

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

A

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

24
Q

how do you increase the surface area of a solid?

A

crush the solid up into smaller pieces

25
Q

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

A

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

26
Q

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

A
  • 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
27
Q

more gas is enclosed when there’s a …

A

quicker reaction

28
Q

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?

A

higher - quicker reaction

29
Q

what does a catalyst do?

A

speed up a reaction

30
Q

what is a catalyst?

A

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

31
Q

how does a catalyst work?

A

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

32
Q

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

A

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

33
Q

where are catalytic converters founds?

A

motor vehicles - vehicle exhausts

34
Q

why do vehicle exhausts use catalytic converters?

A

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

35
Q

what does a catalytic converter do?

A

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

36
Q

when does a catalyst work best in a catalytic converter?

A

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

37
Q

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

A

true

38
Q

how does a higher temperature increase collisions?

A

the particles move quicker so they have more frequent collisions

39
Q

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

A

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

40
Q

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

A

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

41
Q

how does a catalyst increase the number of SUCCESSFUL collisions?

A

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

42
Q

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

A

false - faster collisions increases the rate of reaction

43
Q

how are faster collisions increases?

A

ONLY by temperature

44
Q

reactions can only happen if…

A

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

45
Q

covalent substances are one …

A

non-metal and one metal

additional chemistry (6 decks)

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