2.4.1 Exothermic and Endothermic Reactions

• In exothermic reactions, the energy level of the products is lower than that of the reactants.


  True
• In an energy diagram for an exothermic reaction, ΔH is negative.

  True
• In endothermic reactions, the product energy level is higher
• What is the energy change in an exothermic reaction?

  Releases energy
• Steps to visualize exothermic and endothermic reactions using energy level diagrams:

  1️⃣ Draw the energy level diagram

  2️⃣ Mark the reactants' energy level

  3️⃣ Mark the products' energy level

  4️⃣ Draw an arrow indicating energy change

  5️⃣ Label ΔH as positive or negative
• In exothermic reactions, the products have lower energy than the reactants.


  True
• Exothermic reactions absorb energy from the surroundings.

  False
• Match the reaction type with its example:

  Exothermic ↔️ Combustion of methane

  Endothermic ↔️ Photosynthesis
• Neutralization reactions release energy because they are exothermic
• What two products are formed when calcium carbonate is thermally decomposed?

  CaO and CO₂
• In exothermic reactions, the temperature of the surroundings increases
• Match the reaction characteristic with its type:

  Releases energy ↔️ Exothermic

  Absorbs energy ↔️ Endothermic
• What is an example of an endothermic reaction?

  Photosynthesis
• In exothermic reactions, the surroundings' temperature increases
• What type of energy change occurs in exothermic reactions?

  Releases energy
• Give an example of an exothermic reaction.

  Combustion of methane
• What happens to the surroundings' temperature in endothermic reactions?

  Decreases
• In endothermic reactions, the surroundings' temperature decreases
• In endothermic reactions, the energy level of the products is higher
• In exothermic reactions, ΔH is negative
• In exothermic reactions, the surroundings' temperature increases
• What is an example of an endothermic reaction?

  Photosynthesis
• In an exothermic reaction, the products have lower energy than the reactants.

  True
• In an endothermic reaction, the energy level of the products is higher
• In an exothermic reaction, the surroundings' temperature increases
• The temperature of the surroundings decreases in an endothermic reaction.


  True
• Endothermic reactions release energy to the surroundings.

  False
• The products in an exothermic reaction have lower energy than the reactants.

  True
• Match the energy level diagram with the correct reaction type:

  Diagram showing ΔH < 0 ↔️ Exothermic

  Diagram showing ΔH > 0 ↔️ Endothermic
• What does ΔH < 0 represent in an energy level diagram?

  Exothermic reaction
• What happens to the surroundings' temperature in an exothermic reaction?

  Increases
• Arrange the following characteristics to compare exothermic and endothermic reactions:

  1️⃣ Energy change

  2️⃣ Surroundings' temperature

  3️⃣ Product energy

  4️⃣ Example
• What type of reaction releases energy to the surroundings?

  Exothermic reaction
• Give an example of an exothermic reaction.

  Combustion of methane
• What is the sign of ΔH in an exothermic reaction?

  ΔH < 0
• In an endothermic reaction, energy is absorbed from the surroundings.
• What is released during an exothermic reaction?

  Energy
• Match the reaction type with its example:

  Exothermic ↔️ Combustion of methane

  Endothermic ↔️ Photosynthesis
• Steps to visualize energy changes in a reaction using an energy level diagram:

  1️⃣ Reactants at the top

  2️⃣ Energy barrier to overcome

  3️⃣ Products at the bottom
• What type of energy is usually released in exothermic reactions?

  Heat