1. The change in concentration
of the reactants or products
with time

2. At the end of this presentation, you should be able to:
• define rate of reaction
• identify at least four factors which affect the rate of a
chemical reaction
• explain how the factors cited affect the rate of reaction
• illustrate graphically how a catalyst alters the rate of
reaction
• describe two ways that reaction rate can be measured.

3. For a reaction to occur the particles (atoms,
molecules) have to collide with each other.
The more frequently they collide, the faster the
rate of reaction.
For a reaction to occur the particles must have a
minimum amount of energy. This is called the
ACTIVATION ENERGY.

4. Concentration
Temperature
Surface Area
Pressure
Catalyst

5. • In a concentrated solution, there are more solute
particles per unit volume. Increasing the
concentration, increases the probability of a
collision between the reactant particles since there
are more of them in the same volume.
• Hence, the greater the concentration, the greater
the frequency of collision and the faster the rate of
reaction.

6. • As the temperature increases, the frequency
of collision increases and more particles gain
the activation energy necessary for the
reaction to take place.
• Hence, as temperature increases, the faster
the rate of reaction.

7. • If a solid reactant is broken down into smaller
pieces the rate of reaction increases.
• The particles now have a greater surface area
compared to larger pieces of the solid.
• Hence, there is more chance of a reactant
particle colliding with the solid surface
• As the frequency of collision increases, the
faster the rate of reaction.

8. Pressure is only considered when gases are involved. Look at the
diagrams below and explain how the rate is affected when there
is an increase in pressure.

9. • A catalyst speeds up the rate of a chemical
reaction by providing an alternate pathway of
lower activation energy.
• Since the activation energy is reduced, more
particles will have enough energy to result in a
reaction.

10. • Observe the energy profile diagram for an
endothermic reaction with and without a
catalyst.
• Now draw the energy profile diagram for an
exothermic diagram with and without a catalyst.

11. Two common ways:
• Measuring how fast the products are being
produced.
• Measuring how fast the reactants are being
used up.

12. Visit the following link for more information:
http://www.thestudentroom.co.uk/showthread.php?t=942653

13. Visit the following link for information:
• http://johnwest.edublogs.org/2009/08/18/ncea-level-2-chemistry-rates-
of-reaction-strong-and-weak-acids/

15. 1. Can you account for the shape of this graph?
2. How would the graph look if the same experiment was carried out at a
higher temperature? Discuss your answer with your teacher.