2.4.2 Activation Energy

• Activation energy is the minimum amount of energy required for a chemical reaction to begin
• High activation energies lead to slow reaction rates because more energy is required to initiate the reaction
• Why do reactions with high activation energies proceed slowly?

  Require more energy
• What effect does a catalyst have on activation energy?

  Lowers it
• How does a catalyst lower activation energy?

  Provides an alternate pathway
• What is an example of a biological catalyst in the body?

  Enzymes
• What provides the activation energy needed to light a match?

  Striking the match
• Steps of a catalyzed reaction pathway

  1️⃣ Reactants bind to the catalyst

  2️⃣ Formation of activated complex with lower energy

  3️⃣ Products are formed
• Catalysts provide an alternative reaction pathway with a lower energy barrier
• Lowering activation energy through catalysts increases reaction rates in biological processes like digestion


  True
• Reactions with high activation energies proceed slowly.

  True
• Higher temperature lowers the activation energy of a reaction.


  True
• Factors that lower activation energy result in faster reaction rates.

  True
• A higher temperature lowers activation energy and increases reaction rate.


  True
• Greater surface area of reactants increases reaction rate by lowering activation energy


  True
• Catalysts accelerate chemical reactions without being consumed
• Activation energy is the minimum energy required for a chemical reaction to begin
• Activation energy is inversely proportional to the reaction rate
• What effect does a higher temperature have on the activation energy of a reaction?

  Lowers it
• What role do enzymes play in metabolic processes?

  Lower activation energy
• Order the following factors based on their effect on reaction rate, from fastest to slowest.

  1️⃣ Low activation energy

  2️⃣ High activation energy
• How does a catalyst affect activation energy?

  Lowers activation energy
• The activation energy is inversely proportional to the reaction rate
• Higher temperature lowers activation
• Higher pressure lowers activation
• Uncatalyzed reactions have higher activation energy and slower reaction rates compared to catalyzed reactions

  True
• High activation energy results in a slow reaction rate

  True
• Why does burning wood require a high activation energy?

  Significant heat is needed
• Higher pressure reduces activation energy by compressing reactants


  True
• Arrange the following real-world reactions by their activation energy level from highest to lowest:

  1️⃣ Combustion of fuels

  2️⃣ Rusting of iron

  3️⃣ Polymerization in plastic production

  4️⃣ Photosynthesis

  5️⃣ Enzyme-catalyzed digestion