Topic 7

Question 1

What are enzymes

Answer 1

Biological catalysts

Question 2

Core Practical: Investigate the effects of changing the conditions of a
reaction on the rates of chemical reactions by measuring the production of
a gas and
observing a colour change.

Answer 2

smaller​ ​chips=larger​ ​surface​ ​area=​ ​faster​ ​rate

changing​ ​the​ ​concentration​ ​of​ ​hydrochloric​ ​acid​ greater concentration =​ ​greater​ ​number​ ​of​ ​particles​ ​in​ ​a​ ​given​ ​volume=​ ​faster​ ​rate

Question 3

Rate of reaction​​

Answer 3

Amount of reaction used / time

Amount of product formed overtime

Question 4

​​ ​​ ​​​​ ​​ ​​ ​​ ​​ ​​​​ ​​ ​​ ​​ ​​ ​​ ​​​​ ​​ ​​ ​​​​

Explain how reactions occur when particles collide

Answer 4

Chemical​ ​reactions​ ​only​ ​occur​ ​when​ ​the​ ​reacting​ ​particles​ ​collide​ ​with​ ​enough energy,​ ​the​ ​minimum​ ​amount​ ​of​ ​energy​ ​required​ ​is​ ​called​ ​the​ ​activation​ ​energy.

Question 5

Activation energy

Answer 5

Minimum amount of energy required for reaction to take place.

Question 6

How is the rate of reaction increased when the frequency and/or energy of collisions is increased

Answer 6

To​ ​increase​ ​the​ ​rate​ ​of​ ​a​ ​reaction,​ ​you​ ​need​ ​to​ increase​ ​the frequency/energy​ ​of​ ​collisions,​ ​so​ ​that​ ​more​ ​particles​ ​reach​ ​the​ ​activation​ ​energy
This​ ​can​ ​be​ ​done​ ​by:​ ​increasing​ ​temperature,​ ​pressure,​ ​concentration,​ ​surface area​ ​or​ ​by​ ​using​ ​a​ ​catalyst

Question 7

How does temperature affect rate of reaction?

Answer 7

Increasing​ ​the​ ​temperature​ ​increases​ ​the​ ​rate​ ​of​ ​reaction.​ ​Increasing​ ​temperature​ ​increases​ ​the​ ​kinetic​ ​energy​ ​of particles,​​ ​collide​ ​more​ ​frequently​.

Question 8

Describe a catalyst

Answer 8

Catalysts​ ​are​ ​substances​ ​that​ ​speed​ ​up​ ​chemical​ ​reactions​ ​without​ ​being changed​ ​or​ ​used​ ​up​ ​during​ ​the​ ​reaction.​ ​

Question 9

Explain how the addition of a catalyst increases the rate of a reaction in terms of activation energy

Answer 9

Catalysts​ ​decrease​ ​the​ ​activation​ ​energy, ​so ​more​ ​frequent​ ​successful​ ​collisions and​ ​so​ ​an​ ​increased​ ​rate​ ​of​ ​reaction

Catalysts​ ​lower​ ​the​ ​activation​ ​energy​ ​by providing​ ​a​ different​ ​pathway​ ​for​ ​a​ ​chemical​ ​reaction that​ ​has​ ​a​ ​lower​ ​activation​ ​energy.
​​​​​​ ​​ ​​​​​​ ​​ ​​​​ ​​ ​​ ​​ ​​ ​​ ​​

Question 10

What can enzymes be used for?

Answer 10

Production of ethanol
Yeast produces ethanol ​ ​as​ ​it​ ​is​ ​fermented​ ​from
sugars,​ ​ethanol​ ​is​ ​in​ ​alcoholic​ ​drinks

Question 11

What’s an exothermic reaction?

Answer 11

A reaction where heat energy is given out to surroundings

Question 12

Endothermic reaction

Answer 12

A reaction where heat energy is taken in.

Question 13

Are neutralisation reactions exothermic or endothermic?

Answer 13

Exothermic

Question 14

Are displacement reactions exothermic or endothermic?

Answer 14

Either exothermic or endothermic

Question 15

Is salt dissolving in water either exothermic or endothermic?

Answer 15

Either exothermic or endothermic

Question 16

Are precipitation reactions exothermic or endothermic?

Answer 16

Exothermic

Question 17

How could you measure temp change of neutralisation reactions.

Answer 17

1. Measure temp of solutions
2. Mix both
3. Record highest temp reached.
4. Calculate temp change

Question 18

What enzyme is used to produce ethanol from glucose.

Answer 18

Yeast

Question 19

When measuring temp change in reaction, heat loss means measurements inaccurate, how to minimise this?

Answer 19

Polystyrene cup
Lid on cup
Insulate the beaker with wool

Question 20

In terms of bond energies.

What happens with an exothermic and endothermic reaction.

Answer 20

Exothermic: Energy released from breaking bonds is more than energy used making them.

Exothermic: Energy used from making bonds is more than energy released braking them.

Question 21

2 types of exothermic reactions

Answer 21

Combustion

Neutralisation

Question 22

Examples of endothermic reactions.

Answer 22

Thermal decomposition

Photosynthesis

Question 23

How can energy change in a reaction be calculated with bond energies.

Answer 23

Energy change = Total energy of bonds broken - total energy of bonds made

Question 24

If energy change in a reaction in negative, is it exothermic or endothermic?

Answer 24

Exothermic, heat energy lost to surrounding.

Question 25

How does surface area affect rate of reaction?

Answer 25

Increasing surface area increases rate of reaction. As there are more exposed particles so more frequent successful collisions.

Question 26

How does pressure affect rate of reaction?

Answer 26

Increasing pressure in gaseous reaction increases rate of reaction, there more particles in same volume of air so more frequent successful collisions occur.

Question 27

How does concentration affect rate of reaction?

Answer 27

Increasing concentration in increases rate of reaction, this is because more particles in same volume so more frequent successful collisions occur.