“Reaction Rates”
Review of Alka Seltzer Lab
Collision Theory

Reactions can occur:
fast – such as a firecracker
 Very slow – such as the time it took for
dead plants to make coal
 Very

A “rate” is a measure of the speed of
any change that occurs within an
interval of time
Collision Model
•Key Idea: Molecules must collide
to react.
Factors Affecting Rate
1) Temperature
Increasing temperature always increases the rate
of a reaction.
2) Surface Area
Increasing surface area increases the rate of a
reaction
3) Concentration
Increasing concentration USUALLY increases the
rate of a reaction
4) Presence of Catalysts:
5)Pressure
Increasing the pressure increases the rate of the
reaction.
Catalysts
Catalyst:
A substance that speeds
up a reaction, without being
consumed itself in the reaction
– interfere with the action of a
catalyst; reactions slow or even stop
Inhibitors
Evidence of a Chemical Reaction:
color change
odor change
temperature change
bubbles or gas production
solid formation
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