1. S2 Chemistry
Rates of Reactions

2. 1.1 Reaction Rates Learning Intentions
We are learning about changing the rate of chemical reactions

3. Success Criteria
I can list the 4 methods a reaction can be made faster.
I can describe the effect of a catalyst and an enzyme on a reaction
I can do experiments to show how a reaction’s speed can be increased.
I can evaluate and explain graphs showing speeds of reactions.
I can explain everyday reactions and how to speed them up.

4. Particle Size Apparatus 0.5M hydrochloric acid chalk lumps
chalk powder
2 boiling tubes
test tube rack

5. Particle Size
Method
Two boiling tubes were ¼ filled with 0.5M hydrochloric acid.
4 lumps of chalk were put into one boiling tube
A similar quantity of chalk powder was put into the other boiling tube
Record your results

6. Particle Size
Results
Decreasing the particle size (making the bits smaller) increases the rate of reaction.

7. Temperature Apparatus glucose powder Benedict’s solution Metal beaker
Bunsen and bench mat
Tripod and gauze

8. Temperature
Method
Half fill the metal beaker with water. Heat it with a blue flame until it is boiling then switch off the bunsen.
¼ fill two test tubes with water. Put a spatula of glucose into each test tube.
Put 10 drops of Benedicts into each test tube
Place one of the test tubes into the hot water
Record your results.

9. Temperature
Results
Increasing the temperature increased the rate of the reaction.

10. Concentration Apparatus 0.5M sodium thiosulphate
0.5M hydrochloric acid
100ml beaker
10ml measuring cylinder

11. Concentration
Method
Measure 20ml sodium thiosulphate using a measuring cylinder and pour into a 100ml beaker

12. Concentration
Method
Measure 20ml sodium thiosulphate using a measuring cylinder and pour into a 100ml beaker
Again using a measuring cylinder, measure out the required volume of acid and water and place in a second beaker

13. Concentration
Method
Measure 20ml sodium thiosulphate using a measuring cylinder and pour into a 100ml beaker
Again using a measuring cylinder, measure out the required volume of acid and water and place in a second beaker
Pour one beaker into another and start the timer

14. Concentration
Method
Measure 20ml sodium thiosulphate using a measuring cylinder and pour into a 100ml beaker
Again using a measuring cylinder, measure out the required volume of acid and water and place in a second beaker
Pour one beaker into another and start the timer
Stop the timer when the cross underneath the beaker can no longer be seen

15. Table of Results 1 20 40 0.5 2 16 4 0.4 3 12 8 0.3 0.2 Volume of (cm3)
Sodium thiosulphate
(cm3)
Hydrochloric
Acid
Water
Total
Volume
Conc
HCl
(mol/l)
Time 1 20 40
0.5 2 16 4
0.4 3 12 8
0.3
0.2

16. Concentration 2 Apparatus 1M hydrochloric acid 4M hydrochloric acid
2 boiling tubes
2 pieces of zinc

17. Concentration 2 Method ¼ fill one of the boiling tubes with 1M acid
Place a piece of zinc in each of the boiling tubes and observe the reaction

18. Concentration 2 Results
Increasing the concentration increases the rate of reaction

19. Summary To speed up a chemical reaction you could -
Increase temperature
Increase concentration
Decrease particle size

20. Catalysts
A catalyst is a substance which increases the speed of a chemical reaction without itself being changed.

21. Effect of catalyst
¼ fill a boiling tube with 1M hydrochloric acid

22. Effect of catalyst ¼ fill a boiling tube with 1M hydrochloric acid
Place two pieces of zinc into the boiling tube and observe what happens.

23. Effect of catalyst ¼ fill a boiling tube with 1M hydrochloric acid
Place two pieces of zinc into the boiling tube and observe what happens.
After a few minutes, add a ¼ spatula of powdered copper

24. Effect of catalyst
When copper was added to the test tube the reaction rate was clearly faster. The copper did not take part in the reaction as it could be collected at the end. The copper acted as a catalyst.