““Reaction Rates”Reaction Rates”

Review of Alka Seltzer LabReview of Alka Seltzer Lab

Collision TheoryCollision Theory Reactions can occur:Reactions can occur:

Very fast – such as a firecrackerVery fast – such as a firecracker Very slow – such as the time it took for Very slow – such as the time it took for

dead plants to make coaldead plants to make coal A “rate” is a measure of the speed of A “rate” is a measure of the speed of

any change that occurs within an any change that occurs within an interval of timeinterval of time

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

Factors Affecting RateFactors Affecting Rate1) Temperature

Increasing temperature always increases the rate of a reaction.

2) Surface AreaIncreasing surface area increases the rate of a reaction

3) ConcentrationIncreasing concentration USUALLY increases the rate of a reaction

4) Presence of Catalysts: 5)Pressure Increasing the pressure increases the rate of the

reaction.

CatalystsCatalystsCatalystCatalyst: A substance that speeds : A substance that speeds up a reaction, without being up a reaction, without being consumed itself in the reactionconsumed itself in the reaction

InhibitorsInhibitors – interfere with the action of a – interfere with the action of a catalyst; reactions slow or even stopcatalyst; reactions slow or even stop

Evidence of a Chemical Reaction:Evidence of a Chemical Reaction:

color changecolor changeodor changeodor change

temperature changetemperature changebubbles or gas productionbubbles or gas production

solid formationsolid formation

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