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

Answers1. Using kindling to start a fire

2. Why forest fires are particularly dangerous when weather conditions include high winds.

3. Using Goody’s headache powder, rather than an aspirin tablet

4. Accidentally leaving a gallon of milk on the counter overnight.

Surface AreaSurface Area

Surface AreaSurface Area

ConcentrationConcentration

Temperature

Answers

5. Baking a cake

6. Digesting a cookie

7. Catalytic converter in your car

8. Termites destroying the foundation of a house.

Temperature

Catalyst

Catalyst

Catalyst

In-Class Assignment/Homework

• 23.4 WKT