23.4 Notes

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23.4 Notes Reaction Rates and Energy

• Part B

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Objectives

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

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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

4
Factors affecting reaction (rxn) rates

• Temperature
• Concentration
• Surface area/size
• Catalyst

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Temperature

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

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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.

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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

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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

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Catalyst

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

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Sohow can you speed up a reaction?

• Increase the temperature
• Stir the mixture
• Break the reactants into smaller pieces
• Higher concentration
• Add a catalyst

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Lets Practice

• Identify which factor determines the rate of each
  reaction.
• Temp, Concentration, Surface Area, or Catalyst

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Answers

1. Using kindling to start a fire
2. Why forest fires are particularly dangerous when
   weather conditions include high winds.
3. Using Goodys headache powder, rather than an
   aspirin tablet
4. Accidentally leaving a gallon of milk on the
   counter overnight.

Surface Area
Concentration
Surface Area
Temperature
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Answers

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

Temperature
Catalyst
Catalyst
Catalyst
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In-Class Assignment/Homework

• 23.4 WKT