5.3 The energy change of reactions

• The change in enthalpy (ΔH) for an exothermic reaction is always negative
• The energy level of the products in an endothermic reaction is lower than that of the reactants.

  False
• The energy profile of an exothermic reaction shows that the products have lower energy levels than the reactants
• In an endothermic reaction, the products have higher energy levels than the reactants
• Catalysts lower activation energy and increase the reaction rate
• Catalysts lower activation energy, which increases the reaction rate
• Catalysts provide a different reaction mechanism with a lower activation energy
• The energy level of products in exothermic reactions is lower than reactants.


  True
• In endothermic reactions, the temperature of the surroundings decreases
• Products are the new substances formed as a result of the reaction
• Match the factor with its effect on reaction rate:

  Temperature ↔️ Increases reaction rate

  Catalysts ↔️ Provides lower energy pathway
• Match the factor affecting activation energy with its effect:

  Temperature ↔️ Lowers activation energy

  Catalysts ↔️ Provides alternative mechanism
• Match the reaction type with its energy diagram characteristics:

  Exothermic ↔️ Products have lower energy

  Endothermic ↔️ Products have higher energy
• In an exothermic reaction, the temperature of the surroundings increases.
• The energy diagram for an endothermic reaction shows the products at a higher energy level.
• The temperature of the surroundings increases in an exothermic reaction and decreases in an endothermic reaction.
• An endothermic reaction absorbs heat energy from the surroundings.


  True
• In an exothermic reaction, the surroundings become cooler.

  False
• The energy diagram for an endothermic reaction shows the reactants at a lower energy level, and the products at a higher energy level
• Endothermic reactions absorb heat energy, causing the temperature of the surroundings to decrease
• Steps in using Hess's Law

  1️⃣ Break down the overall reaction into steps with known ΔH values

  2️⃣ Add up the ΔH values for each step
• If the overall ΔH for a reaction is negative, the reaction is exothermic.


  True
• The energy level of the products in an exothermic reaction is higher than that of the reactants.

  False
• What happens to the temperature of the surroundings in an endothermic reaction?

  It decreases
• Match the endothermic reaction with its example:

  Photosynthesis ↔️ Plants absorbing light energy

  Melting of ice ↔️ Solid ice absorbing heat

  Decomposition of hydrogen peroxide ↔️ Breaking down H₂O₂
• Exothermic reactions release heat energy, while endothermic reactions absorb heat energy.

  True
• Endothermic reactions result in a decrease in the temperature of the surroundings.


  True
• What is activation energy?

  Minimum energy for reaction
• Higher activation energy slows down the reaction rate.

  True
• Match the factor with its effect on activation energy:

  Temperature ↔️ Lowers activation energy

  Catalysts ↔️ Provides an alternative pathway
• In exothermic reactions, the temperature of the surroundings increases
• Endothermic reactions absorb heat energy from the surroundings.


  True
• In a chemical reaction, reactants are the starting substances.


  True
• The role of activation energy is to overcome the energy barrier
• Increasing temperature lowers the activation energy.


  True
• Reactions with higher activation energy have a slower reaction rate.


  True
• The energy diagram for an exothermic reaction shows reactants at a higher energy level than products.


  True
• In an endothermic reaction, heat energy is absorbed from the surroundings.


  True
• Match the reaction feature with its type:

  Energy release ↔️ Exothermic

  Energy absorption ↔️ Endothermic
• Exothermic reactions release heat energy to the surroundings, increasing the temperature.


  True