This document discusses the collision theory of chemical reactions. It explains that reactions occur through collisions between reactant particles that provide enough energy to break bonds and form new bonds. The rate of reactions can be increased by factors that increase successful collisions, such as higher temperatures that cause particles to move faster and collide more often and at higher energies, higher concentrations that increase collision frequency, increased surface area of solids to allow more collision sites, and addition of catalysts which lower the activation energy needed for collisions to be successful.
2. The Collision Theory
Link to Simulation of Molecular Motion
1. Matter is moving particles.
2. Temperature increases- particles move faster
-more collisions
-more collision energy.
3. Chemical reactions
-bonds break
-new bonds form
4. Collisions provide the energy.
3. Collision Theory
Most collisions are not successful
Collisions provide the energy required to break bonds.
You need a collision to have a reaction.
5. 2. Sufficient Energy to break the chemical bonds
Activation energy is the minimum amount of energy required for a successful
collision.
6. The Collision Theory can be used to explain how the rate of a reaction can be changed.
And that’s it!
3. Lower activation energy or Ea- low energy collisions are more effective.
2. Harder collisions- greater collision energy
1. More collisions
Reaction rates can increase due to
7. The Collision Theory can be used to explain how the rate of a reaction can be changed.
Harder collisions
More collisions
1. Increasing the temperature increases the rate because there are:
8. 2. Increasing the reactant concentration increases the rate because there are:
More frequent collisions
9. The Collision Theory can be used to explain how the rate of a reaction can be
changed.
The catalyst KI is added to H2O2, food colouring, and dishwashing detergent. The O2
produced makes foam.
Lowers the activation energy or Ea- allowing low energy collisions to be successful
3. Adding a catalyst
Movie
10. The Collision Theory can be used to explain how the rate of a reaction can be
changed.
Lower activation energy or Ea- allowing low energy collisions to be successful
4. Changing the nature of the reactant for a more reactive chemical increases
the rate
11. The Collision Theory can be used to explain how the rate of a reaction can be
changed.
More frequent collisions
5. Increasing the surface area of a solid reactant increases the rate because:
12. Explain each Scenario Using the Collision Theory
The spark provides the Ea and it explodes because it is exothermic
A small spark ignites causes an explosion.
Ea is too high for the room temperature collisions
1. A balloon full of H2 and O2 do not react at room temperature.
13. Explain each Scenario Using the Collision Theory
It burns because it is exothermic
The candle continues to burn
The match provides the Ea
A match causes the candle to burn
Ea is too high for the room temperature collisions
2. A candle does not burn at room temperature
14. Explain each Scenario Using the Collision Theory
3. H2O2 decomposes very slowly at room temperature.
2H2O2(aq) → O2(g) + 2H2O(l)
KI increases the reaction rate dramatically.
Lowers the Ea- allows low energy collisions to be successful
KI is a catalyst as it is not a reactant and it speeds up the rate.
15. Describe and Graph the Relationship between the Following
Ea and the rate
Ea
Rate
Decreasing the Ea increases the rate- inverse.
16. Describe and Graph the Relationship between the Following
Temperature and the rate
Temp
Rate
Increasing the temperature increases the rate- direct.
17. Describe and Graph the Relationship between the Following
Concentration and the rate
Conc
Rate
Increasing the concentration increases the rate- direct.
18. Describe and Graph the Relationship between the Following
Ea and the temperature
Ea
Temp
No relationship!
The only way to change the Ea is by adding a catalyst!
19. Which factors increase the percentage of successful collisions?
I. Increasing temperature
II. Increasing concentration
III. Increasing surface area
IV. Adding a catalyst
