“Reaction Rates”

1. “Reaction Rates” Review of Alka Seltzer Lab

2. Collision Theory • Reactions can occur: • Very fast – such as a firecracker • Very slow – such as the time it took for dead plants to make coal • A “rate” is a measure of the speed of any change that occurs within an interval of time

3. Collision Model • Key Idea: Molecules must collide to react.

4. Factors Affecting Rate • Temperature • Increasing temperature always increases the rate of a reaction. • Surface Area • Increasing surface area increases the rate of a reaction • Concentration • Increasing concentration USUALLY increases the rate of a reaction • Presence of Catalysts: • Pressure Increasing the pressure increases the rate of the reaction.

5. Catalysts • Catalyst: A substance that speeds up a reaction, without being consumed itself in the reaction • Inhibitors – interfere with the action of a catalyst; reactions slow or even stop

6. Evidence of a Chemical Reaction:color changeodor changetemperature changebubbles or gas productionsolid formation

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