5.3 The energy change of reactions

• Exothermic reactions release energy, often as heat
• What type of reaction absorbs energy from the surroundings?

  Endothermic
• Endothermic reactions release energy into the surroundings.

  False
• What do energy profile diagrams show?

  Energy changes
• In an exothermic reaction, the energy of the products is higher than the energy of the reactants.

  False
• In an endothermic reaction, the energy of the products is higher than the energy of the reactants
• What is the minimum energy required to start a reaction called?

  Activation energy
• Reactions with lower activation energies are generally slower.

  False
• Reactions with higher activation energies are generally slower to occur
• Match the reaction type with an example:

  Exothermic ↔️ Combustion

  Endothermic ↔️ Photosynthesis
• In an endothermic reaction, the energy of the products is higher than the energy of the reactants
• What type of activation energy is associated with exothermic reactions?

  Lower
• Exothermic reactions release energy
• Match the type of reaction with its characteristic:

  Exothermic ↔️ Releases energy

  Endothermic ↔️ Absorbs energy
• Reactions with higher activation energies have slower rates
• Which type of reaction has a lower activation energy, exothermic or endothermic?

  Exothermic
• A positive ΔH indicates an exothermic reaction.

  False
• What does a negative enthalpy change indicate about a reaction?

  Releases energy
• Endothermic reactions increase the temperature of their surroundings.

  False
• In an exothermic reaction, the energy of the products is lower
• What happens to the energy of products compared to reactants in an exothermic reaction?

  Lower
• Exothermic reactions release energy, while endothermic reactions absorb energy.


  True
• In an exothermic reaction, how does the energy of the products compare to the reactants?

  Lower
• Exothermic reactions have lower activation energy compared to endothermic reactions.
• In an exothermic reaction, the energy of the products is lower than the reactants, and the reaction releases energy.


  True
• What is the minimum energy required to start a reaction called?

  Activation energy
• Which type of reaction has a lower activation energy: exothermic or endothermic?

  Exothermic
• What is the formula to calculate the enthalpy change (ΔH) of a reaction?

  $\Delta H =$$\Sigma E(products) - \Sigma E(reactants)$
• An example of an exothermic reaction is combustion.
• What is the ΔH for the reaction where the energy of reactants is 350 kJ and the energy of products is 250 kJ?

  -100 kJ
• What happens to the temperature of the surroundings in an exothermic reaction?

  Increases
• Exothermic reactions release energy in the form of heat.


  True
• In an endothermic reaction, the temperature of the surroundings decreases
• What do energy profile diagrams represent in chemical reactions?

  Energy changes
• An upward slope in an energy profile diagram indicates an endothermic
• Reactions with higher activation energies proceed more quickly.

  False
• If ΔH is negative, the reaction is exothermic
• A negative enthalpy change indicates an exothermic reaction.

  True
• What type of reaction releases energy into the surroundings?

  Exothermic
• Exothermic reactions cause a decrease in temperature of the surroundings.

  False