Chapter 12.1 and 12.4 of A Natural Approach to Chemistry Reaction Rates

Rates of Reactions How fast does a reaction occur?

Why Do We Care? Sometimes we need reactions to happen quickly. Sometimes we need to slow reactions down.

Why Do We Care? How do we know if a reaction is going to occur quickly or slowly? Better yet, how can we control the rate of a reaction?

Rate of Reaction Rate of Reaction - how fast a reaction occurs -how quickly the amount of reactants __________ -how quickly the amount of products __________ decrease increase

Collision Theory Collision Theory – In order to react, reactant molecules must collide with each other How does this relate to reaction rates? In order to increase reaction rate, we must increase the number of collisions.

Factors Affecting Reaction Rate 1) Temperature – hotter temperatures mean: ____________ molecules molecular collisions ___________ Reaction rate __________ faster increase increases

Factors Affecting Reaction Rate Low ConcentrationHigh Concentration Which of these will have more collisions?

Factors Affecting Reaction Rate 2) Concentration – higher concentration means: _______ reactant molecules molecular collisions ___________ Reaction rate __________ more increase increases

Factors Affecting Reaction Rate Low Surface AreaHigh Surface Area Which of these will have more collisions?

Factors Affecting Reaction Rate 3) Surface Area – higher surface area means: _______ reactant molecules available for collisions molecular collisions ___________ Reaction rate __________ more increase increases

Factors Affecting Reaction Rate

4) Catalyst – molecule that ____________ the reaction rate without getting used up in the reaction itself How does it do this? - It lowers the activation energy of the reaction increases