Reaction Profiles and Activation Energy · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Reading the hill a reaction climbs

Science · Matter & Materials · ages 15-16
Name ______________________   Date ____________

  1. The products sit below the reactants. What kind of reaction is it?

    • Endothermic
    • One with no energy change
    • Exothermic

  2. On a reaction profile, what does the top of the hump mark?

    • The activation energy
    • The overall energy change
    • The final temperature

  3. An exothermic reaction still needs some energy put in to start.

    Circle one:   True   False

  4. Reactants sit at 0 and products at -80. What is the overall energy change?

    • +40
    • -80
    • +120

  5. A profile labels reactants at 0 and the peak at 120. What is the activation energy?

    • 80
    • 120
    • 200

  6. A beaker reaction warms up as it runs. Which profile fits?

    • Products below the reactants
    • Products above the reactants
    • Reactants and products level

  7. On a profile, the overall change is the drop from the peak to the products.

    Circle one:   True   False

  8. Methane burning gives out heat, yet it needs a spark. Why?

    • The spark adds the missing oxygen
    • The spark cools the products down
    • The spark lifts a few molecules over the hump
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Reading the hill a reaction climbs W1-mt_6LtFkXn_xQ-s1

  1. Exothermic · A drop from reactants to products releases heat, which is exothermic.
  2. The activation energy · The climb from reactants to the peak is the activation energy.
  3. True · Reactants must climb the activation hump before they can release heat.
  4. -80 · Products minus reactants is -80 minus 0, which is -80.
  5. 120 · Peak minus reactants is 120 minus 0, which is 120.
  6. Products below the reactants · Warming means heat left the mixture, so products sit lower.
  7. False · The overall change runs from reactants to products, not from the peak.
  8. The spark lifts a few molecules over the hump · The spark pays the activation fee for a few molecules, and their heat pays for the rest.
Worksheet · LightMySky