1. Collision Theory
Factors affecting rate
Particle size affects rate

2. 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

3. Factors affecting Rate of reaction
1. Concentration
2. Temperature
3. Particle size
4. Nature of reactants
5. Presence of a catalyst

4. Effect of Particle size on rate
Smaller particles have a greater surface area
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5. Surface area, collisions & rate
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6. Investigate the effect of particle size on reaction rate
HCl +
CaCO3
CaCl2 +
H2O +
CO2
The rate of release of CO2 gas can be used to monitor the progress of the reaction

7. Add the HCl to a large chips of CaCO3 in the flask
As CO2 is released the mass of the flask drops
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8. 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

9. Result
Finely divided particles react faster than large particles