Collision Theory

Question 1

What is collision theory? The theory that …

So to react particles must…?

Answer 1

…rate of reaction depend son how often and how hard reacting particles collide with each other

Collide together with enough energy to react

Question 2

More collisions …. the …. of ….

Answer 2

increases the rate of reaction

Question 3

The effects of temp, surface area, and concentration can be explained by what?

Answer 3

How often the reacting particles collide successfully

Question 4

What happens to the number of collisions under higher temperature?
What happens to the particles when temperature is increased?
So how does this affect their collisions?

Answer 4

The increase in frequency
They move faster
They occur more frequently, they collide more often

Question 5

What happens to the number of collisions under higher concentration or pressure?
What happens if a solution is made more concentrated?
What does increasing the pressure in a gas mean?

Answer 5

They increase
There are more particles of reactant between the water molecules in the aqueous, which makes collisions of the actual reactant particles more likely therefore more frequent.
The particles are closer together so there will be more frequent collisions.

Question 6

What happens to the number of collisions when there is a larger surface area?
If one of the …. is a ….. then breaking it up into … pieces will … its …. …. area.
What happens if this happens?

Answer 6

They increase
reactants, solid, small, increase, total surface
The particles around the solid in the solution will have more area to work on so there’ll be more frequent collisions

Question 7

Faster collisions …?
Increasing the temperature causes…
Reactions only happen when…

Answer 7

increase the rate of reaction
… faster collisions
… the particles collide with enough energy

Question 8

What does higher temperature do to the collisions?

Answer 8

It increases the energy of the collisions because it makes all the particles move faster

Question 9

The minimum amount of energy needed by the particles to react is called what?
At …. temps there will be more particles ….. with enough … to make the reaction happen.

Answer 9

The activation energy

higher, colliding, energy

Question 10

What is a catalyst?

Answer 10

A substance which speeds up a reaction, without being used up or changed in the reaction

Question 11

How does a solid catalyst work?

Answer 11

It gives the reacting particles a surface to stick to therefore increasing the number of successful collisions between particles, so it speeds up the reaction

Question 12

How do catalysts help to reduce costs in an industrial reaction? (3)

Answer 12

1. They increase the rate of reaction saving a lot of money as the machine doesn’t need to operate for so long to produce the same amount of product.
2. The reactions will work at a lower temperature reducing the energy needed, good for cost and sustainable development
3. They never get used up

Question 13

What are the disadvantages to using a catalyst industrially? (4)

Answer 13

1. Expensive to buy
2. Often need to be removed from the product to be cleaned
3. Different reactions require different catalysts meaning many will be needed for a plant
4. They can be poisoned by impurities and stop working so the reaction mixture must be kept clean

Question 14

Whenever chemical reactions occur, energy ….

Answer 14

…is transferred to or from the surroundings

Question 15

In an exothermic reaction … is …. ….

Answer 15

heat is given out

Question 16

What is an exothermic reaction?

Answer 16

One that gives energy out to the surroundings usually in the form of heat and is usually shown by a temperature rise.

Question 17

What are three examples of an exothermic reaction?

Answer 17

Burning fuels
Neutralisation reactions
Oxidation reactions

Question 18

What happens in the exothermic reaction where fuel is burned? (simple)

Answer 18

Combustion, it gives out a lot of heat

Question 19

What happens in the exothermic reaction of neutralisation?

Answer 19

Acid + alkali gives out a lot of heat

Question 20

What happens in the exothermic reaction of oxidation, using an example?

Answer 20

Sodium + water produces heat, the sodium emits heat and moves about on the surface of the water as it’s oxidised.

Question 21

How do hand warmers work?

How do self heating hot chocolate and coffee cups work?

Answer 21

An exothermic reaction of iron and air, with a salt catalyst generates heat.
They rely on exothermic reactions in the chemcials in the bases of the cans

Question 22

In an endothermic reaction heat is….

Answer 22

taken in

Question 23

What is an endothermic reaction?

Answer 23

One that take sin energy from the surroundings usually in the form of heat and is usually shown as a fall in temp.

Question 24

How common are endothermic reactions?

What is a common example, of one?

Answer 24

Less common than exo.

Thermal decomposition.

Question 25

Give an example of a thermal decomposition reaction?

1. What is supplied
2. What are the reactants and what happens (symbol equation)

Answer 25

1. Heat must be supplied to make the calcium carbonate decompose to make quicklime.
2. CaCo3 (to)= CaO + CO2

Question 26

What is one every day use of an endothermic reaction?

Answer 26

Sports injury packs take in heat making their surroundings very cold, more convenient than ice.

Question 27

What energy transfer is in a reversible reaction?

Answer 27

Endothermic and exothermic, one in one direction, one in the other

Question 28

The energy absorbed by the …… ….. is … to the energy released by the …. ….. .

Answer 28

endothermic reaction is equal, exothermic reaction

Question 29

What is a good example of a reversible reaction?

What happens using what energy transfers?

Answer 29

Thermal decomposition of hydrated copper sulphate
Hydrated copper sulphate to anhydrous copper sulphate and water, exothermic, gives out energy, the other way round takes it in.

Question 30

Describe the thermal decomposition of hydrated copper sulphate… (2)

Answer 30

Heating the blue copper crystals evaporates the water and leaves white crystals, this is endothermic.
If you add some water to the white crystals you get the blue ones again, this is exothermic.