Science lesson plan · 10th grade (Year 11 in England) · 60 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 · 6 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.
- Is this exothermic or endothermic: magnesium reacting with acid? (exothermic / endothermic) → exothermicPrompt: Does it give out heat or take heat in?
- The temperature of a reaction mixture changes from 21 °C to 38 °C. What is the temperature change? (Use a minus sign for a fall.) → 17 °CPrompt: Change = final temperature − starting temperature.
- In an exothermic reaction, the energy of the products is… (higher than the energy of the reactants / zero / lower than the energy of the reactants / exactly the same as the reactants) → lower than the energy of the reactantsPrompt: Energy has been given out to the surroundings.
Hook · 6 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 · 12 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 · 12 min
- Do these together. Students try each step on whiteboards before you reveal it.
- Use the hints as prompts rather than giving the answer.
- On a reaction profile, the reactants are at 50 kJ, the peak is at 90 kJ and the products are at 20 kJ. What is the overall energy change, in kJ? (Use a minus sign if energy is released.) → -30 kJPrompt: energy change = energy of products − energy of reactants
- Reactants: 40 kJ. Peak of the profile: 165 kJ. Products: 10 kJ. What is the activation energy, in kJ? → 125 kJPrompt: Activation energy is the minimum energy needed to start the reaction.
You do: independent practice · 17 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 8 questions are on the student sheet below, with answers in the key.
Exit ticket · 7 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- On a reaction profile, the reactants are at 80 kJ, the peak is at 180 kJ and the products are at 100 kJ. What is the overall energy change, in kJ? (Use a minus sign if energy is released.) → 20 kJPrompt: energy change = energy of products − energy of reactants
- Why does a mixture of methane and air not burn until a spark is added? (The spark removes carbon dioxide / The spark provides the activation energy / Methane is endothermic / The spark adds oxygen) → The spark provides the activation energyPrompt: Reactions need a minimum energy to start.
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