Science lesson plan · 7th grade (Year 8 in England) · 60 minutes
Thermal decomposition of carbonates
Chemical reactions, acids and bases
CCSS NGSS.MS-PS1-2England: KS3 Chemistry: Chemical reactions
Objective and success criteria
Students will: Thermal decomposition of carbonates.
- 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: Conservation of mass in reactions
Leads to: the next skill in this area.
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 (Conservation of mass in reactions). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- In a sealed flask, 19 g of substance A reacts completely with 11 g of substance B. 10 g of product D forms along with product C. What mass of C forms, in g? → 20 gPrompt: Total mass of reactants = total mass of products.
- 25 g of calcium carbonate is heated in an open tube until it all breaks down. 14 g of calcium oxide is left. What mass of carbon dioxide escaped, in g? → 11 gPrompt: Mass seems to be lost. Where did it go?
- Why is mass conserved in a chemical reaction? (Atoms are only rearranged; none are made or destroyed / Reactions happen too fast to change mass / Energy is conserved / Products are always the same substances as reactants) → Atoms are only rearranged; none are made or destroyedPrompt: Count the atoms on both sides of an equation.
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: Thermal decomposition of carbonates. 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: Calcium carbonate is heated strongly and breaks down. What are the products?
- Step 1: metal carbonate → metal oxide + carbon dioxide
- Step 2: So the answer is: calcium oxide + carbon dioxide
- Answer: calcium oxide + carbon dioxide
- 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.
- Magnesium carbonate is heated strongly and breaks down. What are the products? (magnesium hydroxide + water / magnesium oxide + oxygen / magnesium + carbon dioxide / magnesium oxide + carbon dioxide) → magnesium oxide + carbon dioxidePrompt: A carbonate contains a metal, carbon and oxygen.
- Green copper carbonate is heated and turns black. What is the black solid? (copper / carbon / copper oxide / copper sulfate) → copper oxidePrompt: Carbon dioxide has left the solid.
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.
- When 100 g of calcium carbonate is heated, it forms 56 g of calcium oxide and 44 g of carbon dioxide. What mass of carbon dioxide forms from 20 g of calcium carbonate, in g? → 8.8 gPrompt: The masses stay in the same proportion.
- Making cement is responsible for a large share of global CO₂ emissions. Why? (Heating limestone releases CO₂, and burning fuel to heat kilns releases more / Concrete gives off CO₂ forever / Cement is made from coal / Cement absorbs oxygen) → Heating limestone releases CO₂, and burning fuel to heat kilns releases morePrompt: Two sources of CO₂ are involved.
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: Conservation of mass in 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
- 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-7.
Free lesson plan from eurekami.com/lesson-plan-builder