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Science lesson plan · 7th grade (Year 8 in England) · 30 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 · 4 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.
  1. In a sealed flask, 17 g of substance A reacts completely with 13 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.
  2. 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?
  3. Magnesium ribbon is burned in a crucible. The ash weighs more than the ribbon did. Why? (Oxygen atoms from the air have combined with the magnesium / Heat has mass / The crucible got heavier / Burning creates new atoms) → Oxygen atoms from the air have combined with the magnesiumPrompt: What is the product of burning magnesium?

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: Thermal decomposition of carbonates. 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: 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 · 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. Calcium carbonate is heated strongly and breaks down. What are the products? (calcium + oxygen + carbon / calcium oxide + carbon dioxide / calcium + carbon dioxide / calcium hydroxide + water) → calcium oxide + carbon dioxidePrompt: A carbonate contains a metal, carbon and oxygen.
  2. 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 / Cement is made from coal / Cement absorbs oxygen / Concrete gives off CO₂ forever) → Heating limestone releases CO₂, and burning fuel to heat kilns releases morePrompt: Two sources of CO₂ are involved.

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. Copper carbonate is heated strongly and breaks down. What are the products? (copper + oxygen + carbon / copper hydroxide + water / copper oxide + oxygen / copper oxide + carbon dioxide) → copper oxide + carbon dioxidePrompt: A carbonate contains a metal, carbon and oxygen.
  2. 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 250 g of calcium carbonate, in g? → 110 gPrompt: The masses stay in the same proportion.

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

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Thermal decomposition of carbonates

Name

Date

Score/ 6

  1. Question 1

    Why is limestone (calcium carbonate) heated in kilns?

    • A. to make quicklime (calcium oxide) for cement and building
    • B. to make it heavier
    • C. to make oxygen
    • D. to turn it into gold

  2. Question 2

    Zinc carbonate is heated strongly and breaks down. What are the products?

    • A. zinc hydroxide + water
    • B. zinc + oxygen + carbon
    • C. zinc oxide + carbon dioxide
    • D. zinc oxide + oxygen

  3. Question 3

    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 250 g of calcium carbonate, in g?

    Answerg

  4. Question 4

    Making cement is responsible for a large share of global COâ‚‚ emissions. Why?

    • A. Cement is made from coal
    • B. Heating limestone releases COâ‚‚, and burning fuel to heat kilns releases more
    • C. Concrete gives off COâ‚‚ forever
    • D. Cement absorbs oxygen

  5. Question 5

    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 50 g of calcium carbonate, in g?

    Answerg

  6. Question 6

    How can you show that carbon dioxide is given off when a carbonate is heated?

    • A. bubble the gas through limewater, which turns cloudy (milky)
    • B. hold a glowing splint in it, which relights
    • C. hold a lit splint in it, which gives a squeaky pop
    • D. smell it

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Answer key: Thermal decomposition of carbonates

  1. 1. A. to make quicklime (calcium oxide) for cement and building

  2. 2. C. zinc oxide + carbon dioxide

  3. 3. 110 g

  4. 4. B. Heating limestone releases COâ‚‚, and burning fuel to heat kilns releases more

  5. 5. 22 g

  6. 6. A. bubble the gas through limewater, which turns cloudy (milky)