1. Rates of Reaction
6 March 2023

2. Learning Objectives
3.9 describe experiments to investigate the effects of changes in surface area of a solid,
concentration of solutions, temperature and the use of a catalyst on the rate of a reaction
3.10 describe the effects of changes in surface area of a solid, concentration of solutions,
pressure of gases, temperature and the use of a catalyst on the rate of a reaction
3.11 explain the effects of changes in surface area of a solid, concentration of solutions,
pressure of gases and temperature on the rate of a reaction in terms of particle collision
theory
3.12 know that a catalyst is a substance that increases the rate of a reaction, but is chemically
unchanged at the end of the reaction

3. Learning Objectives
3.13 know that a catalyst works by providing an alternative pathway with lower activation
energy
3.14C draw and explain reaction profile diagrams showing ΔH and activation energy
3.15 practical: investigate the effect of changing the surface area of marble chips and of
changing the concentration of hydrochloric acid on the rate of reaction between marble
chips and dilute hydrochloric acid
3.16 practical: investigate the effect of different solids on the catalytic decomposition of
hydrogen peroxide solution

4. Rates of Reaction
The rate of reaction is
the rate at which
products are formed, or
the rate at which
reactions are used up, in
a reaction.

5. Rates of Reaction
The ACTIVATION
ENERGY is the
minimum amount of
energy required to
cause the reaction
to happen.
Chemical reactions
will only occur when
the reacting
particles collide with
each other with
sufficient energy so
they react.
There are FIVE very important factors which can affect the rate of reaction.

6. Rates of Reaction
Temperature
Pressure
(of gases)
Concentration
Surface
Area
Catalyst
https://wordwall.net/resource/
53457112/rates-of-reaction

7. Rates of Reaction
Question:
How can we explain the
rates of reaction using
kinetic molecular theory?

8. Rates of Reaction
Kinetic theory is all
about the random
movement of
particles
Kinetic theory assumes that particles
are in constant random motion

9. Rates of Reaction
Kinetic theory is all
about the random
movement of particles
Kinetic theory assumes that particles are
in constant random motion
!
And there will be collisions!
It’s these collisions that are the cause of
chemical reactions.

10. Rates of Reaction
1. Temperature of the Reactants
HEAT
Cold conditions,
particles have little
energy, move slowly
and collide
infrequently and less
successfully
When heated,
particles have more
energy, move faster,
collide frequently and
more successfully
High
temperature
Low
temperature

11. Rates of Reaction
2. Concentration of the Dissolved Reactants
Particles are spread
out and will collide
with each other less
often, with fewer
successful collisions
Particles are crowded
close together, so
collide more often,
with more successful
collisions
High
concentration
Low
concentration

12. Rates of Reaction
3. Pressure (in gases)
Particles are spread out
and will collide with each
other less often, with
fewer successful collisions
Particles are pushed closer
together, they collide more
frequently, with more
successful collisions
High
pressure
Low
pressure

13. Rates of Reaction
4. Surface area of solid reactants
Large particles have a small
surface area in relation to
volume – less particles exposed,
fewer collisions, slow reaction
Smaller particles have a larger
surface area in relation to
volume- more particles exposed,
more collisions, faster reaction
large
surface
area
small
surface
area

14. Rates of Reaction
5. Using a catalyst
A catalyst is a substance which increases the rate of a
chemical reaction without being used up itself. It can
be used over and over again.

15. Activation Energy
What’s this ACTIVATION
ENERGY all about?
The ACTIVATION ENERGY is the
relatively small amount of energy
needed to start a chemical reaction

16. Activation Energy

17. Activation Energy

18. Rates of Reaction
Experiments
1. Surface
area
Increasing the surface area of reactants increases the rate of
reaction

19. Rates of Reaction
Experiments
2.
Concentration

20. Rates of Reaction
Experiments
2.
Concentration

21. Rates of Reaction
Experiments
2.
Concentration
Volume of thiosulphate
Time
for
cross
to
disappear
As the concentration of sodium thiosulphate increases, so the time taken
decreases – the rate of reaction gets faster.

22. Rates of Reaction
Experiments
3.
Temperature
Tempera
ture of
reaction
mixture
(oC)
Reaction time (secs)
Average
reaction
time (secs)
Experiment
1
Experiment
2
Experiment
3
40 24 25 25 25
50 22 20 20 21
60 17 16 16 16
70 12 11 11 11
80 7 7 8 7

23. Rates of Reaction
Experiments
3.
Temperature
Tempera
ture of
reaction
mixture
(oC)
Reaction time (secs)
Average
reaction
time (secs)
Experiment
1
Experiment
2
Experiment
3
40 24 25 25 25
50 22 20 20 21
60 17 16 16 16
70 12 11 11 11
80 7 7 8 7
As the temperature increases so the
time taken for the cross to disappear
decreases – the reaction gets faster.

24. Rates of Reaction
Experiments
4. Catalysts

25. Rates of Reaction
Experiments
4. Catalysts

26. Rates of Reaction
Experiments
4. Catalysts

27. In this lesson we have covered:
Rates of Reaction
Activation Energy
Rates of Reaction Experiments
Rates of Reaction