5.1.1 Defining exothermic and endothermic reactions

• What does it mean when products have less energy than reactants in exothermic reactions?

  Extra energy is given off as heat
• What are endothermic reactions?

  Chemical reactions that absorb energy
• How does an exothermic reaction feel to the touch?

  Feels warm
• What is the chemical equation for the combustion of wood?

  Wood + Oxygen -> Carbon Dioxide + Water + Heat
• What happens to energy during an exothermic reaction?

  Energy decreases as heat is released
• What are the key features of endothermic reactions compared to exothermic reactions?

  • Energy: Absorbed vs. Released
  • Energy levels: Reactants have less energy vs. Products have less energy
  • Temperature change: Feels cold vs. Feels warm
• How do exothermic reactions feel to the touch?

  They feel warm due to heat transfer
• What is the key difference between exothermic and endothermic reactions?

  Energy changes between reactants and products
• What happens to the energy of reactants in endothermic reactions?

  Reactants need to gain energy for the reaction
• What is the energy level of products in exothermic reactions compared to reactants?

  Lower than reactants
• What is the relationship between the activation energy and the potential energy of the reactants and products in an exothermic reaction?

  The activation energy is higher than the potential energy of the reactants
• How does an endothermic reaction feel to the touch?

  Feels cold
• How does energy flow in exothermic reactions?

  Out to surroundings
• What is the name of the type of reaction shown in the right diagram?

  Endothermic reaction
• How do endothermic reactions differ from exothermic reactions in terms of energy transfer?

  Endothermic reactions absorb energy, exothermic release it
• Compare the properties of exothermic and endothermic reactions.

  • Exothermic:
  • Energy flow: Out to surroundings
  • Product energy: Lower than reactants
  • Temperature change: Feels warm
  • Activation energy: Required to start

  
  

  • Endothermic:
  • Energy flow: In from surroundings
  • Product energy: Higher than reactants
  • Temperature change: Feels cold
  • Activation energy: Required to start
• What are the key differences between exothermic and endothermic reactions?

  • Exothermic reactions release energy, endothermic reactions absorb energy
  • Exothermic reactions have a higher activation energy than the potential energy of the reactants, endothermic reactions have a lower activation energy than the potential energy of the reactants
  • Products of exothermic reactions have lower potential energy than the reactants, products of endothermic reactions have higher potential energy than the reactants
• How does the energy of products compare to reactants in endothermic reactions?

  Products have more energy than reactants
• What is the name of the type of reaction shown in the left diagram?

  Exothermic reaction
• How do the energy profiles of exothermic and endothermic reactions differ?

  • Exothermic reactions have a downward sloping energy profile, with the products having lower potential energy than the reactants
  • Endothermic reactions have an upward sloping energy profile, with the products having higher potential energy than the reactants
• What is the energy level of products in endothermic reactions compared to reactants?

  Higher than reactants
• If a reaction feels cold to the touch, what type of reaction is it likely to be?

  Endothermic reaction
• What determines whether a reaction is exothermic or endothermic?

  The overall energy change
• What temperature change is associated with endothermic reactions?

  They feel cold
• How does energy flow in endothermic reactions?

  In from surroundings
• What is required to start both exothermic and endothermic reactions?

  Activation energy
• What do exothermic reactions release to the surroundings?

  Energy in the form of heat