GCSE CHEMISTRY

Question 1

Rates of reactions : what is the rate of chemical reactions

Answer 1

The rate of chemical reactions is how fast the reactants are changed into products

Question 2

What is an example of a slow chemical reaction

Answer 2

One of the slowest reactions is the dusting of iron

Question 3

What are examples of slow reactions that include chemical weathering

Answer 3

The examples are like acid rain damage to limestone buildings

Question 4

What is an examples of moderate speed reactions

Answer 4

An example of moderate speed reaction would be metal magnesium reacting with an acid to produce a gentle stream of bubbles

Question 5

What type of reaction if burning

Answer 5

Burning is a fast reaction

Question 6

What are explosives

Answer 6

Burning is a fast reaction but explosions are even faster and release a lot of gas.

Question 7

What is the speed of an explosive

Answer 7

Explosive reactions are all over in a fraction of a second

Question 8

How do u calculate the speed of a reaction

Answer 8

Amount of reactant/product formed
———————————————-
Time

Question 9

What does the steeper line on the graph show

Answer 9

The steeper line on the graph shows how fast that rate of reaction is

Question 10

How is the quickest reaction shown

Answer 10

The quickest reaction is shown to have the steepest line and become flat in the least time

Question 11

What happens over time ???

Answer 11

Over time the line becomes less steep as true reactant is used up

Question 12

What must particles do in order to react

Answer 12

Particles must collide with enough energy in order to react

Question 13

How are rate of reactions explained

Answer 13

They are explained perfectly by the Collision theory

Question 14

What time the 3 ways to measure the rate of reactions

Answer 14

1) precipitation and colour change
2) change in mad and colour change
3) the volume of gas of given off

Question 15

Precipitation and colour change

Answer 15

1) the visual changes are when the solution changes from a transparent to opaque
2) I set the mark through the solution and measure how long it takes to disappear - the faster the mark disappears the quicker the reaction
3) if the reactant is flourless the product is colourless u can’t time how long it takes to lose or agin colour

Question 16

what is the collision frequency?

Answer 16

the collision frequency of the reacting particles (how often they collide) the more collisions there are the faster the reaction is.

Question 17

what happens if you double the rate of the reaction?

Answer 17

doubling the frequency of the collisions doubles the rate

Question 18

what is transferred during the collisions

Answer 18

energy is transferred during a collision. they have to collide with enough energy for the collision to be successful

Question 19

what is activation of energy?

Answer 19

it is the minimum amount of energy that particles need to react.

Question 20

why do particles need energy?

Answer 20

they need energy to break bonds in the reactions and start the reaction.

Question 21

what are the 4 things that rate of reactions depend on?

Answer 21

1) temperature
2) concentration of the solution or the pressure of gas
3) surface are- this changes depending on the size of the lumps of a soild
4) the presence of a catalyst.

Question 22

what does more collisions do?

Answer 22

more collisions increase the rate of reaction

Question 23

how can all the four term be explained

Answer 23

all the four methods of increasing the rate of reaction can be explained in terms of increasing the umber of successful collisions between the reactions of particles.

Question 24

what does increasing the temperature do?

Answer 24

when the temperature in increased, the particles all move faster.
if they move faster, they’re going to collide more frequently. also the faster they move the more energy they have, so more of the collisions will have enough energy to make the reaction happen.

Question 25

what does increasing the concentration or pressure do?

Answer 25

if solution is more concentrated, this means that there are more particles knocking about in the same volume of water. (or other solvent)

Question 26

what happens to the particles when pressure is increased?

Answer 26

when pressure is increased , it means that the same number of particles occupied a smaller space.
this makes the collision more frequent.

Question 27

what happens when u increase the surface area?

Answer 27

this means that for the same volume of the solid, the particles around it will have more area to work on - so there will be collisions more frequently.

Question 28

how is the surface area increased?

Answer 28

if one of the reactant is a solid , then breaking it up into smaller pieces will increase the surface area to volume reaction.

Question 29

what is a catalyst?

Answer 29

it is a substance that speeds up the reaction, without being used up in the reaction itself.

Question 30

why are different catalyst used for different reactions?

Answer 30

because they work by decreasing the activation energy needed for the reaction to occur.

Question 31

what are biological catalysts?

Answer 31

they are enzymes. they catalyses reactions in living things.