Presentation on theme: "Section 2.8—Speeding Up A Reaction"— Presentation transcript:
1 Section 2.8—Speeding Up A Reaction How can we make those antacid reactions occur faster?
2 Kinetics & Reaction Rates Kinetics – Study of the rates of reactionsReaction Rate – Rate at which reactants produce products
3 Collision TheoryCollision Theory – Defines 3 circumstances to be met for a reaction to occur.1Reactants must collide2Collision must be at the correct orientationCollision must have minimum energy for reaction to occur3Only a small number of collisions meet the requirements and result in a reaction
4 Collisions Must OccurIn order for two molecules to react, they must come in contact with one anotherNOFThere’s no way they’ll ever react if they don’t run into one another!
5 Collision with Correct Orientation For a collision to result in a chemical reaction, it must occur with the correct orientationNOFThis is not the correct orientation. The reaction will not happen.
6 Collision with Correct Orientation For a collision to result in a chemical reaction, it must occur with the correct orientationFNONOFFBut not every collision produces a reaction—they must collide in the correct orientation to reactThis is the correct orientation. The reaction will happen.
7 Collision with Enough Energy For a collision to result in a chemical reaction, it must occur with the minimum energy for reactionNOFThe collision does not have enough energy to produce a reaction
8 Collision with Enough Energy For a collision to result in a chemical reaction, it must occur with the minimum energy for reactionFNONOFFThis collision had more energy (faster moving molecules). A reaction will occur..
9 Activation EnergyMinimum energy for reaction to occur during a collision
10 Reaction Coordinate Diagram Reaction coordinate diagrams show the energy changes throughout the reactionActivated complex(Also called the transition state)Activation EnergyProductsEnergyEnergy change for reactionReactantsReaction proceeds
11 Activated Complex What is an “activated complex”? F N O N O F F Reaction proceedsEnergyActivated ComplexReactantsF2NO2F2 + NO2ProductsF + FNO2FNONOFF
13 Surface Area of Reactants How does the surface area of the reactants affect the reaction rate?More reactants can collide at the same time and a fraction of those will result in reactionLarger surface area means more particles can come in contact with each other at the same timeReactants must collide in order to reactAs surface area increases, reaction rate increases
14 Concentrations of Reactants How does the concentration of reactants affect the reaction rate?Only a small fraction of the collisions meet the requirements and result in a reactionIf more collisions occur, more will meet the requirements and result in a reactionMore reactants mean more collisions will occurAs reaction concentration increases, reaction rate increases
15 For most reactions, as temperature increases, reaction rate increases How does temperature affect the reaction rate?With higher energy molecules, collisions will have higher energy and more often result in reactionIf molecules are at a higher temperature, they have a higher average kinetic energyReactants must collide with at least energy equal to the activation energyFor most reactions, as temperature increases, reaction rate increases
16 CatalystsCatalysts – Substance that increases the rate of reaction without being used upA + B + C D + C“C” is the catalyst…it is present in the beginning and in the endEnzymes are catalysts in the body
17 CatalystsHow do catalysts help speed up the reaction without being used?They increase the chances that a collision will successfully produce a reactionFor example, catalysts hold one or more of the reactants in place to allow collisions to occur with the correct orientationCatalysts make a successful collision more likely. They lower the activation energy by allowing reactants to react in a different way, or by holding reactants in place for the reaction. Once they’ve done their job, they are released and available to “help” another reactant.Once the reaction has occurred, the catalyst releases the molecule(s) and finds another one to help
18 Catalysts & Reaction Diagrams Reaction Path without catalystReaction Path with catalystEnergyReaction proceedsCatalysts lower the activation energy of the reaction by letting it proceed in a different way.With lower activation energy, a higher percentage of collisions will be successful (they don’t need to collide with as much energy to be successful)