4/11/12 - Bellringer What does a catalytic converter do?

23.4 Notes – Reaction Rates and Energy Part B

Objectives Describe the factors that affect reaction rate. Discuss the effects of catalysts and inhibitors on the speed of chemical reactions

Reaction rate How quickly a reaction occurs The time it takes reactants to turn into products The change in concentration of reactants and products over time

Factors affecting reaction (rxn) rates Temperature Concentration Surface area/size Catalyst

Temperature The higher the temperature, the faster the molecules are moving The faster the molecules are, the more collisions there are

Temperature Increasing the temperature increases the kinetic energy of each particle. The more energy, the more likely the particles will have enough energy to achieve the activation energy.

Concentration The more particles there are within a given space, the more likely a collision is to occur This increases the frequency of collisions Ex - eature=related eature=related

Surface Area How much of a material is exposed –The larger the surface area of a reactant, the greater the number of particles that are exposed for reaction –This increases the frequency at which particles collide

Surface Area Example 4x4 cube vs. 4, 2x2 cubes

Catalyst vs. Inhibitor A catalyst speeds up a chemical reaction without itself being permanently changed Lowers the activation energy An inhibitor prevents or slows a chemical reaction

Methods to Speed Up a Reaction Increase the temperature Stir the mixture Break the reactants into smaller pieces Use higher concentrations Add a catalyst

Let’s Practice Identify which factor determines the rate of each reaction. –Temp, Concentration, Surface Area, or Catalyst

Practice 1.Using kindling to start a fire SURFACE AREA 2.Why forest fires are particularly dangerous when weather conditions include high winds. CONCENTRATION 3.Grain elevator explosions SURFACE AREA 4.Using Goody’s headache powder, rather than an aspirin tablet SURFACE AREA

Practice 5.Accidentally leaving a gallon of milk on the counter overnight. TEMPERATURE 6.Baking a cake TEMPERATURE 7.Digesting a cookie CATALYST 8.Catalytic converter in your car CATALYST 9.Termites destroying the foundation of a house. CATALYST

In-Class Assignment/Homework Finish WKT QUIZ FRIDAY –Be able to… –Identify the source of energy changes in chemical reactions. –Compare and contrast endothermic and exothermic reactions. –Describe the factors that affect reaction rate. –Discuss the effects of catalysts and inhibitors on the speed of chemical reactions –Balance equations and identify reaction types