Collision Theory
Factors affecting rate
Investigate how concentration
affects rate
Collision Theory
1.
For a reaction to occur the particles
must collide
2.
The colliding particles must have a
minimum energy called the
Activation Energy
Collisions & Activation Energy
Next slide
Factors affecting Rate of reaction
1.
Concentration
2. Temperature
3.
Particle size
4.
Nature of reactants
5.
Presence of a catalyst
Effect of concentration on rate
Increasing concentration increases the rate
By increasing the number of collisions
Investigate the effect of
concentration on reaction rate
HCl + Na2S2O3
NaCl + SO2 + H2O + S
The formation of a pale yellow precipitate of
sulphur can be used to monitor the progress of
the reaction
To investigate the effect of
concentration on reaction rate
Next slide
Add the HCl to the Na2S2O3 in the flask
Record the time taken for the X to disappear
Repeat with different concentrations of Na2S2O3
Inverse the time to get the rate
Effect of concentration on rate
Conclusion
?
R
A
T
E
1
Time
Rate is directly
proportional to
concentration
CONCENTRATION
Collision Theory
Factors affecting rate
Particle size
affects rate
Collision Theory
1.
For a reaction to occur the particles
must collide
2.
The colliding particles must have a
minimum energy called the
Activation Energy
Factors affecting Rate of reaction
1.
Concentration
2. Temperature
3.
Particle size
4.
Nature of reactants
5.
Presence of a catalyst
Effect of Particle size on rate
Smaller particles have a greater surface area
Next slide
Surface area, collisions & rate
Next slide
Investigate the effect of
particle size on reaction rate
HCl + CaCO3
CaCl2 +
H 2O +
CO2
The rate of release of CO2 gas can be used to
monitor the progress of the reaction
Add the HCl to a large chips of CaCO3 in the flask
As CO2 is released the mass of the flask drops
Next slide
Record the time taken for the release of CO2 to end
( No further mass loss)
Repeat using the same mass of powdered CaCO3
and the same volume of HCl
And the same concentration of HCL
Result
Finely divided particles react faster than large particles
Collision Theory
Factors affecting rate
Investigate how temperature
affects rate
Collision Theory
1.
For a reaction to occur the particles
must collide
2.
The colliding particles must have a
minimum energy called the
Activation Energy
Factors affecting Rate of reaction
1.
Concentration
2. Temperature
3.
Particle size
4.
Nature of reactants
5.
Presence of a catalyst
Temperature, Collisions &
Activation Energy
Next slide
Effect of temperature on rate
Increasing temperature increases the rate
By increasing the number of collisions / sec
More of the colliding particles have E Act
Investigate the effect of
temperature on reaction rate
HCl + Na2S2O3
NaCl + SO2 + H2O + S
The formation of a pale yellow precipitate of
sulphur can be used to monitor the progress of
the reaction
To investigate the effect of
temperature on reaction rate
Next slide
Add the HCl to the Na2S2O3 in the flask
Record the temperature after mixing
Record the time taken for the X to disappear
Inverse the time to get the rate
Repeat at different temperatures
Next slide
Effect of temperature on rate
Conclusion
?
R
A
T
E
1
Rate increases
with increasing
temperature
Time
TEMPERATURE
Effect of temperature on rate
What is the
main factor
increasing rate
between
A and B
R
A
T
E
1
Time
B
A
TEMPERATURE
Rate increases
due to increased
collisions /sec
Effect of temperature on rate
R
A
T
E
C
What other
factor caused
the large rate
increase
between
B and C
1
Time
B
TEMPERATURE
More colliding
particles have
E Act
Nature of
reactants
affect the rate
Collision Theory
1.
For a reaction to occur the particles
must collide
2.
The colliding particles must have a
minimum energy called the
Activation Energy
Factors affecting Rate of reaction
1.
Concentration
2. Temperature
3.
Particle size
4.
Nature of reactants
5.
Presence of a catalyst
Nature of reactants affects rate
Ionic reactions are fast
+
Na Cl
+
Ag+NO
3
= Ag+Cl +
Na+NO
3
Mix solutions of sodium chloride and silver nitrate
A precipitate of silver chloride forms instantly
Ions are free to move in solution....no bonds to break
Sodium chloride + Silver Nitrate
next
Covalent reactions are slower than ionic
HCl + Na2S2O3
NaCl + SO2 + H2O + S
The pale yellow precipitate of sulphur forms slowly
as covalent bonds in the sodium thiosulfate must first
be broken before the reaction can occur
End