The document discusses collision theory, which states that chemical reactions occur through collisions between reactant molecules. It explains that for a reaction to happen upon collision, the molecules must possess sufficient kinetic energy (known as activation energy) and be properly oriented. Only when these two conditions are met will an "effective collision" lead to the formation of products through an activated complex. The document also discusses factors that affect reaction rates such as concentration and temperature based on collision theory.

1. Collision Theory of Chemical
Reaction
This theory states that for reactions to occur,
molecules, atoms, or ions must first collide.
It also explains how collision between reactant
molecules may or may not result in a successful
chemical reaction.

2. Collision Theory

3. Effective collisions between molecules, which
result in the formation of products, only occur
when the following two conditions are met:
(a) The colliding molecules should possess a
minimum kinetic energy, known as activation
energy, to start a chemical reaction.
(b) the reactant molecules should be in correct
orientation when they collide.

5. Activation
energy
- is the energy
required to
initiate a reaction
and force the
reactants to form
an activated
complex.

6. Energy is always part of a chemical
reaction.
The heat of reaction is used in many
things.
As more substances are involved in a
chemical reaction, more energy is either
absorbed or released to the environment.

7. In chemical reactions, bond breaking
and forming occurs.
1. Bond breaking - energy is
absorbed
2. Bond forming - energy is released

8. The net amount of energy in the breaking and
forming of bonds determines if a reaction is:
•Exothermic – describes a process or reaction that
releases energy from the system to its
surroundings.
•Endothermic - describes a process or reaction
that absorbs energy from the surroundings to its
system.

9. Factors affecting
reaction rates
1. Concentration of reactants
2. Temperature

10. 1. Concentration of reactants
In collision theory, an increase in reactant
concentration ensures that there will be
more collisions between particles.
This also increases the probability rate of
effective collisions.

11. 2. Temperature
In collision theory, increasing the
temperature of the reactants increases the
kinetic energy that it possesses, thereby
increasing the number of collisions and giving
enough energy to overcome the activation
energy.

12.  Acid Rain –is rain that is more acidic
than normal.
 It is a precipitation that has a pH of less
than that of natural rainwater (which is
about 5.6 due to dissolved carbon
dioxide).

13. •Sulfur dioxide and nitrogen oxides, the
major sources of acid rain.
•It is formed when sulfur dioxides and
nitrogen oxides, as gases or fine particles in
the atmosphere, combine with water vapor
and precipitate as sulfuric acid or nitric acid
in rain, snow, or fog.

15. Acid rain has been the leading significant
cause of destruction in our environment.
In infrastructure, it is the cause of
corrosion of metals in alloys like steel in
buildings, bridges, and transport vehicles.

16. Materials with historical and cultural
values such as monuments and statues
are also destroyed by acid rain.
They are mostly made up of limestone
and marble which like metals form a
chemical reaction with acids, lead to
their dissolution.

18. Decay of Stonework
German sandstone statue from 1702 photographed in 1908 (left) and
1969 (right).

19. Marine life is also affected by acid rain.
It causes the pH of bodies of water to
decrease; this change in pH will increase
marine life mortality, retard fish growth,
decrease egg production and embryo
survival.

21. Acid rain also tends to dissolve
vital minerals in the soil. Crops
grown in these depleted soils
give poor yields, if they grow at
all.

22. Causes of Acid Rain
The principal cause of acid rain is from
human sources
 Industrial factories, power-generating
plants and vehicles
 Sulphur dioxide and oxides of nitrogen are
released during the fuel burning process (i.e.
combustion)

25. In urban areas, the main source of acid rain is from
automobiles.
Other sources are thermal power plants and coal
mining industries.
Gas emissions like CO2, CO, SO2, NO2, and NO from
these sources react with water vapor in the air
producing acids. Rain contaminated with these acids are
what we know now as acid rain.