# Reaction Rates. Rate of a Chemical Reaction: Is a measure of how quickly or slowly the reaction occurs (Science 10 Curriculum Sask Learning) To measure.

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Reaction Rates

Rate of a Chemical Reaction: Is a measure of how quickly or slowly the reaction occurs (Science 10 Curriculum Sask Learning) To measure you must consider: – How much product is formed – How much reactant is used up – Time interval

Kinetic Molecular Theory: “Particles are constantly moving and that they move more quickly at higher temperatures” (Nelson Science 10 260) Molecules moving slowly or stable molecules will be less likely to react after a collision If molecules move quickly and hit harder there is a greater chance of a collision

Collision Model: “The rate of reaction is affected by the number of [effective] collisions of reactant molecules” (261) – Consider that if all collisions were effective, the reaction would be instantaneous Increasing Reaction Rate : (261) – Increase the [number of] collisions – Increase the fraction of effective collisions

Factors Affecting Reaction Rates Temperature: – Heat increases the reaction rate As temperature increases, molecule speed increases = increased chance of a collision = increased chance of an effective collision that can cause a reaction – Cool temperatures can slow reactions Keep your food fresh longer

Factors Affecting Reaction Rates Concentration: – If you have more reactants = increased chance of a collision = greater chance of a reaction – Increased concentration increases the reaction rate

Factors Affecting Reaction Rates Surface Area: – The amount of a reactant that is on the outside; what will come into contact with the other reactant – The greater the surface area the better the chance of an effective collision = increased reaction rate

Factors Affecting Reaction Rates Catalyst: – “Is a substance that increases the rate of a chemical reaction without being consumed by the reaction” (263) – An easier way for the reaction to occur – Increases the fraction of effective collisions – Lowers the activation energy – Catalysts are often inorganic – Enzymes are organic catalysts

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