C3.2.2 Calculating Energy Changes

• What is the term for the difference between the energy required to break bonds in reactants and the energy released when forming bonds in products?

  Energy change
• What happens to the temperature of the surroundings in an exothermic reaction?

  Increases
• Photosynthesis is an example of an endothermic
• Endothermic reactions absorb energy and decrease the temperature of the surroundings.


  True
• In which type of reaction does energy flow from the reaction to the surroundings?

  Exothermic
• What does a negative $\Delta H$ value indicate in a chemical reaction?


  Exothermic reaction
• What is the formula used to calculate the energy change ($\Delta H$) in a chemical reaction?


  $\Delta H =$$H_{products} - H_{reactants}$
• $H_{reactants}$ represents the total energy of the reactants
• Match the reaction type with its energy change and temperature effect:

  Exothermic ↔️ \Delta H < 0, temperature increases

  Endothermic ↔️ \Delta H > 0, temperature decreases
• $\Delta H$ is calculated using the bond energies of reactants and products
• What is the sign of $\Delta H$ in endothermic reactions?


  Positive
• Order the examples of exothermic and endothermic reactions:

  1️⃣ Combustion

  2️⃣ Neutralisation

  3️⃣ Thermal decomposition
• In exothermic reactions, heat is released and $\Delta H$ is negative.


  True
• $\Delta H$ is calculated as the difference between the total energy of the products and the total energy of the reactants
• What is the sign of $\Delta H$ in exothermic reactions?


  Negative
• Bond energies are used to calculate $\Delta H$ in chemical reactions.


  True
• Match the reaction type with its $\Delta H$ and temperature change:


  Exothermic ↔️ \Delta H < 0, temperature increases

  Endothermic ↔️ \Delta H > 0, temperature decreases
• Combustion is an example of an exothermic
• Endothermic reactions absorb energy from the surroundings, causing the temperature to decrease.


  True
• What happens to the energy and temperature in an exothermic reaction?

  Energy released, temperature increases
• Neutralisation is an example of an exothermic
• What is the energy change in an endothermic reaction?

  Positive
• A positive $\Delta H$ value indicates an endothermic reaction.


  True
• $H_{products}$ represents the total energy of the products
• In an exothermic reaction, $\Delta H$ is negative and the temperature increases.


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

  It decreases
• What is the sign of $\Delta H$ in exothermic reactions?


  Negative
• Match the comparison features with the correct reaction type:

  Exothermic ↔️ Releases heat, \Delta H < 0

  Endothermic ↔️ Absorbs heat, \Delta H > 0
• $\Delta H$ is calculated using the bond energies of reactants and products
• What happens to the temperature of the surroundings in an exothermic reaction?

  It increases
• A negative $\Delta H$ indicates an exothermic reaction.


  True
• What is the sign of $\Delta H$ in endothermic reactions?


  Positive
• The combustion of methane has a $\Delta H$ of -890 kJ/mol.
• The combustion of methane is an exothermic reaction.


  True