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Science lesson plan · 10th grade (Year 11 in England) · 30 minutes

Reaction profiles: energy change and activation energy

Chemical reactions, acids and bases

CCSS NGSS.HS-PS1-4England: GCSE Combined Science: Energy changes

Objective and success criteria

Students will: Reaction profiles: energy change and activation energy.

  • I can answer questions on today's skill on my own, without help.
  • I can explain each step and say why it works.
  • I can check my answer and spot a mistake.

Before and after

Needs first: Exothermic and endothermic reactions

Leads to: Predict how an equilibrium shifts (Le Chatelier); Calculate energy changes from bond energies

Materials: Teacher demo or video, Indicator color chart, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).

Warm-up · 4 min

  • Quick retrieval from earlier learning (Exothermic and endothermic reactions). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. Is this exothermic or endothermic: neutralising an acid with an alkali? (exothermic / endothermic) → exothermicPrompt: Does it give out heat or take heat in?
  2. The temperature of a reaction mixture changes from 19 °C to 4 °C. What is the temperature change? (Use a minus sign for a fall.) → -15 °CPrompt: Change = final temperature − starting temperature.
  3. In an exothermic reaction, the energy of the products is… (lower than the energy of the reactants / higher than the energy of the reactants / zero / exactly the same as the reactants) → lower than the energy of the reactantsPrompt: Energy has been given out to the surroundings.

Hook · 3 min

  • Drop an antacid tablet in water (or show a clip) and ask whether a new substance is being made.
  • Share the objective: Reaction profiles: energy change and activation energy. Read the success criteria together.

I do: model it · 7 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: On a reaction profile, the reactants are at 80 kJ, the peak is at 220 kJ and the products are at 140 kJ. What is the overall energy change, in kJ? (Use a minus sign if energy is released.)
  • Step 1: 140 − 80 = 60
  • Step 2: Positive: energy is taken in (endothermic).
  • Step 3: So the answer is: 60 kJ
  • Answer: 60 kJ
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 6 min

  • Do these together. Students try each step on whiteboards before you reveal it.
  • Use the hints as prompts rather than giving the answer.
  1. On a reaction profile, the reactants are at 100 kJ, the peak is at 220 kJ and the products are at 40 kJ. What is the overall energy change, in kJ? (Use a minus sign if energy is released.) → -60 kJPrompt: energy change = energy of products − energy of reactants
  2. Reactants: 90 kJ. Peak of the profile: 140 kJ. Products: 60 kJ. What is the activation energy, in kJ? → 50 kJPrompt: Activation energy is the minimum energy needed to start the reaction.

You do: independent practice · 7 min

  • Students work on the student sheet. Circulate and check the first two answers of every student early.
  • Students who finish: write a question of their own for a partner, with the answer.

The 6 questions are on the student sheet below, with answers in the key.

Exit ticket · 3 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. Self-heating cans for camping use a reaction between calcium oxide and water. What type of reaction is this? (endothermic / thermal decomposition / electrolysis / exothermic) → exothermicPrompt: The can gets hot.
  2. Reactants: 140 kJ. Peak of the profile: 290 kJ. Products: 110 kJ. What is the activation energy, in kJ? → 150 kJPrompt: Activation energy is the minimum energy needed to start the reaction.

Watch out for

  • Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
  • Remembering facts without the reason: ask "why?" and "what is the evidence?"

Support and stretch

Support

  • Review first: Exothermic and endothermic reactions.
  • Use concrete materials: teacher demo or video.
  • Give the first step of each question, or a partly worked example to finish.
  • Pair with a confident partner for the guided practice.

Stretch

  • Move on to: Predict how an equilibrium shifts (Le Chatelier); Calculate energy changes from bond energies.
  • Explain a common mistake in writing and how to fix it.
  • Write a word problem that uses today's skill, then solve a partner's.

Homework and more practice

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-10.

Free lesson plan from eurekami.com/lesson-plan-builder

eurekami

Reaction profiles: energy change and activation energy

Name

Date

Score/ 6

  1. Question 1

    Reactants: 40 kJ. Peak of the profile: 110 kJ. Products: 10 kJ. What is the activation energy, in kJ?

    AnswerkJ

  2. Question 2

    Self-heating cans for camping use a reaction between calcium oxide and water. What type of reaction is this?

    • A. electrolysis
    • B. endothermic
    • C. thermal decomposition
    • D. exothermic

  3. Question 3

    On a reaction profile, the reactants are at 100 kJ, the peak is at 230 kJ and the products are at 130 kJ. What is the overall energy change, in kJ? (Use a minus sign if energy is released.)

    AnswerkJ

  4. Question 4

    Reactants: 60 kJ. Peak of the profile: 185 kJ. Products: 10 kJ. What is the activation energy, in kJ?

    AnswerkJ

  5. Question 5

    Why does a mixture of methane and air not burn until a spark is added?

    • A. The spark adds oxygen
    • B. The spark provides the activation energy
    • C. The spark removes carbon dioxide
    • D. Methane is endothermic

  6. Question 6

    On a reaction profile, the reactants are at 120 kJ, the peak is at 200 kJ and the products are at 160 kJ. What is the overall energy change, in kJ? (Use a minus sign if energy is released.)

    AnswerkJ

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Answer key: Reaction profiles: energy change and activation energy

  1. 1. 70 kJ

  2. 2. D. exothermic

  3. 3. 30 kJ

  4. 4. 125 kJ

  5. 5. B. The spark provides the activation energy

  6. 6. 40 kJ