Endothermic and Exothermic Reactions

Learning Intentions

  • To understand the difference between endothermic and exothermic reactions
  • To be able to graph the change in energy during a chemical or physical reactions


Notes

Endothermic and Exothermic Reactions (12:20)


Questions

  1. What is the activation energy for a chemical reaction?
  2. Draw the graph of potential energy vs. time for the following reactions, and identify each as endothermic or exothermic:
    1. TNT exploding
    2. Sweat evaporating
    3. Baking bread
    4. Splitting a molecule of nitrogen gas
    5. Snow forming in clouds
  3. Watch the following video. What can you say about the activation energy for exploding nitroglicerine?
    Free Range Chemistry 37 - Nitroglycerin Bang (2:30)

  4. Why can an endothermic reaction can be dangerous to touch?
  5. Why can an exothermic reaction can be dangerous to touch?
  6. In an endothermic reaction, where does the energy come from? Where does it go?
  7. In an exothermic reaction, where does the energy come from? Where does it go?
  8. Extension: How does a fridge use endothermic and exothermic state changes to achieve cooling?