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 Video info

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

Catalyst Speeds up a chemical reaction without itself being permanently changed Lowers the activation energy An inhibitor prevents or slows a chemical reaction

So…how can you speed up a reaction? Increase the temperature Stir the mixture Break the reactants into smaller pieces Higher concentration Add a catalyst

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

Answers Using kindling to start a fire Why forest fires are particularly dangerous when weather conditions include high winds. Using Goody’s headache powder, rather than an aspirin tablet Accidentally leaving a gallon of milk on the counter overnight. Surface Area Concentration Surface Area Temperature

Answers Baking a cake Digesting a cookie Catalytic converter in your car Termites destroying the foundation of a house. Temperature Catalyst Catalyst Catalyst

In-Class Assignment/Homework 23.4 WKT