Science lesson plan · 8th grade (Year 9 in England) · 45 minutes
Exothermic and endothermic reactions
Chemical reactions, acids and bases
CCSS NGSS.MS-PS1-6CCSS NGSS.HS-PS1-4England: KS3 Chemistry: EnergeticsEngland: KS4 Combined Science: Energy changes in chemistry
Objective and success criteria
Students will: Exothermic and endothermic reactions.
- 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: Reactants, products and word equations
Leads to: Rates of reaction; Reaction profiles: energy change and activation energy
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 · 5 min
- Quick retrieval from earlier learning (Reactants, products and word equations). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- Complete the word equation: iron + oxygen → ___ (carbon dioxide / iron chloride / iron oxide / iron carbonate) → iron oxidePrompt: A metal reacting with oxygen makes a metal oxide.
- Calcium carbonate is heated strongly: calcium carbonate → calcium oxide + ___ (oxygen / carbon dioxide / water / hydrogen) → carbon dioxidePrompt: What is left when you take CaO away from CaCO₃?
- Word equations: which statement is NOT true? (Reactants are written on the left of the arrow. / Products are the substances you start with. / Combustion is a reaction with oxygen. / Incomplete combustion can produce carbon monoxide, a poisonous gas.) → Products are the substances you start with.Prompt: Which side of the arrow is which?
Hook · 5 min
- Drop an antacid tablet in water (or show a clip) and ask whether a new substance is being made.
- Share the objective: Exothermic and endothermic reactions. Read the success criteria together.
I do: model it · 10 min
- Work through the example out loud, saying why you do each step, not just what you do.
- Example: Is this exothermic or endothermic: thermal decomposition of calcium carbonate?
- Step 1: Endothermic reactions take in energy from the surroundings, so the temperature falls.
- Step 2: So the answer is: endothermic
- Answer: endothermic
- Pause after each step and ask a student to say what comes next.
We do: guided practice · 10 min
- Do these together. Students try each step on whiteboards before you reveal it.
- Use the hints as prompts rather than giving the answer.
- Is this exothermic or endothermic: thermal decomposition of calcium carbonate? (exothermic / endothermic) → endothermicPrompt: Does it give out heat or take heat in?
- The temperature of a reaction mixture changes from 20 °C to 17 °C. What is the temperature change? (Use a minus sign for a fall.) → -3 °CPrompt: Change = final temperature − starting temperature.
You do: independent practice · 10 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 · 5 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- Breaking chemical bonds… (has no energy change / gives out energy (exothermic) / takes in energy (endothermic) / creates new atoms) → takes in energy (endothermic)Prompt: You have to put energy in to pull atoms apart.
- The temperature of a reaction mixture changes from 21 °C to 31 °C. What is the temperature change? (Use a minus sign for a fall.) → 10 °CPrompt: Change = final temperature − starting temperature.
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: Reactants, products and word equations.
- 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: Rates of reaction; Reaction profiles: energy change and activation energy.
- 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-8.
Free lesson plan from eurekami.com/lesson-plan-builder