Science lesson plan · 7th grade (Year 8 in England) · 45 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 · 5 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, 12 g of substance A reacts completely with 32 g of substance B. 7 g of product D forms along with product C. What mass of C forms, in g? → 37 gPrompt: Total mass of reactants = total mass of products.
- 50 g of calcium carbonate is heated in an open tube until it all breaks down. 28 g of calcium oxide is left. What mass of carbon dioxide escaped, in g? → 22 gPrompt: Mass seems to be lost. Where did it go?
- Why is mass conserved in a chemical reaction? (Reactions happen too fast to change mass / Atoms are only rearranged; none are made or destroyed / 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 · 5 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 · 10 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 · 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.
- Calcium carbonate is heated strongly and breaks down. What are the products? (calcium hydroxide + water / calcium + oxygen + carbon / calcium oxide + oxygen / calcium oxide + carbon dioxide) → calcium oxide + carbon dioxidePrompt: A carbonate contains a metal, carbon and oxygen.
- Why is limestone (calcium carbonate) heated in kilns? (to turn it into gold / to make it heavier / to make quicklime (calcium oxide) for cement and building / to make oxygen) → to make quicklime (calcium oxide) for cement and buildingPrompt: Thermal decomposition makes an oxide.
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.
- Calcium carbonate is heated strongly and breaks down. What are the products? (calcium + carbon dioxide / calcium oxide + carbon dioxide / calcium + oxygen + carbon / calcium hydroxide + water) → calcium oxide + carbon dioxidePrompt: A carbonate contains a metal, carbon and oxygen.
- Making cement is responsible for a large share of global CO₂ emissions. Why? (Cement absorbs oxygen / Concrete gives off CO₂ forever / Heating limestone releases CO₂, and burning fuel to heat kilns releases more / Cement is made from coal) → 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