Topic 5 - Chemical Reactions

Question 1

What is an exothermic reaction ?

Answer 1

A reaction which overall gives out more energy to the surrounding areas (in the form of heat) shown by a rise in temperature

Question 2

What is an endothermic reaction?

Answer 2

A reaction which overall takes in energy from the surroundings in the form of heat, shown by a fall in temperature.

Question 3

Give an example of an exothermic reaction

Answer 3

Combustion Explosions

Question 4

Give an example of an endothermic reaction

Answer 4

Photosynthesis Ammonium nitrate dissolving in water

Question 5

Are endothermic or exothermic reactions more common?

Answer 5

Exothermic

Question 6

What do you need to break bonds in a chemical reaction?

Answer 6

Energy

Question 7

Which type of reaction is this?

Answer 7

Endothermic

Question 8

What is the best way to measure temperature change in a reaction?

Answer 8

Take the temperature of each of the reactants and try to get them the same. Then put them in a polystyrene cup in a beaker with cotton wool in to insulate it then put a lid on the cup to prevent evaporation. Measure the temperature of the solution at the end.

Question 9

Give an example of a slow reaction

Answer 9

The rusting of iron

Question 10

Give an example of a moderate speed reaction

Answer 10

Metal reacting with acid

Question 11

Give an example of a fast reaction

Answer 11

Explosion

Question 12

What four things can affect the rate of reaction?

Answer 12

Temperature Concentration Catalyst Surface area

Question 13

Why does temperature affect the rate of reaction?

Answer 13

The hotter the reaction the faster it is. The heat gives particles more energy so the move around more and it is more likely to get frequent successful collisions. It also provides them with enough energy to break the bonds.

Question 14

Why does concentration affect the rate of reaction?

Answer 14

The higher the concentration the faster the reaction. There are more particles so there will be a higher frequency of successful reactions.

Question 15

how does a catalyst affect the rate of reaction

Answer 15

A catalyst will speed up the rate of reaction by lowering the amount of energy required by the reactants to react. They increase the frequency of successful collisions.

Question 16

How does surface area affect the rate of reaction?

Answer 16

The bigger the surface area the faster the reaction. There are more particles near the surface so more frequent successful reactions will take place.

Question 17

Describe an experiment to test the effects of concentration or surface area on rate of reaction.

Answer 17

Put HCL and marble chips in a conical flask and but a gas syringe on it. Time how long it takes to get to a certain volume of gas. For concentration - repeat with different concentrations of HCL. For surface area - repeat with same mass but different sized marble chips.

Question 18

Describe an experiment that can be used to show the effect of temperature on rate of reaction

Answer 18

But a flask on a piece of paper with a cross on it. Mix Sodium Thiosulfate and HCL together and time how long it takes the cross to be no longer visible. Change temperature of sodium Thiosulfate to see the affects.

Question 19

Give an example of where a catalyst converter can be found

Answer 19

Vehicle exhaust. They are used to increase the rate that carbon monoxide and unused fuel react with oxygen to produce carbon dioxide and water. The catalyst has a large surface area and works best at high temperatures.

Question 20

What is collision theory?

Answer 20

more collisions increases the rate of reactions

Question 21

Name two common processes that use catalysts

Answer 21

the Haber process to make ammonia (iron)

hydrogenation of margarine (nickel)