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The limestone cycle

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Teaching notes

Slides 3 – 11The section takes students through the limestone cycle by making model compounds. The models don’t distinguish between ionic and covalent bonds, different coloured bond pieces could be used to show ionic and covalent bonds if appropriate for the group.

Students could work in pairs or independently. Each pair will need the following Molymod pieces.

-I x calcium atom-2 x carbon atoms-6 x oxygen atoms-2 x hydrogen atoms-12 x bonds

Click the boxes on each slide to reveal what the model compounds should look like.

Slide 12 – 17Check students knowledge of the cycle using the interactive quiz. Depending on the group you can choose to reveal multiple choice options if and when it’s appropriate.

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calcium carbonate

calcium oxide

calcium hydroxide

calcium hydroxide solution

heat

add waterfilter

add CO2

The limestone

cycle

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O

OO C

Ca

CaCO3

Make a model of limestone (calcium carbonate) using the Molymod atoms.

Answer

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C OOCa O

Task

Break down your calcium carbonate model to make calcium oxide and carbon dioxide.

CaCO3

heat

When calcium carbonate is heated it breaks down to form calcium oxide and carbon dioxide. This is called thermal decomposition.

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CaO

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calcium carbonate

calcium oxide

calcium hydroxide

calcium hydroxide solution

heat

add waterfilter

add CO2

The limestone

cycle

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calcium oxide

CaO

O

H

H

TaskWhen calcium oxide is added to water it forms calcium hydroxide.Combine your models of calcium oxide and water together to make calcium hydroxide.

water

Ca(OH)2

CaO O

H

H

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CaO

O

H

H

calcium hydroxide

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calcium hydroxide solution

calcium carbonate

calcium oxide

calcium hydroxide

heat

add waterfilter

add CO2

The limestone

cycle

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O

O

0 C Ca

Task

If carbon dioxide is bubbled through calcium hydroxide solution (limewater)It turns milky because calcium carbonate is formed. Combine your models of calcium hydroxide and carbon dioxide to form calcium carbonate.

CO2Ca(OH)2

CaCO3

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O

O

0 C Ca

Limestone!

O

H

H

Task

Which atoms are left over?

Which compound can you make from them?

Answer

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calcium carbonate

calcium oxide

calcium hydroxide

calcium hydroxide solution

heat

add waterfilter

add CO2

The limestone

cycle

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calcium carbonate

calcium oxide

calcium hydroxide

calcium hydroxide solution

heat

add waterfilter

add CO2

The limestone

cycle

Click to reveal

Click to reveal

Click to reveal

Click to revealClick to reveal

Click to reveal

Click to revealClick to reveal

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A: carbon malagnite

B: calcium carbonate

C: calcium oxide

D: calcium hydroxide

calcium carbonate

What is the chemical name for limestone?

Answer

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A: Melting a solid by heating.

B: Throwing rubbish away.

C: Breaking a chemical compound down by cooling.

D: Breaking a chemical compound down by heating.

What is thermal decomposition?

Breaking a chemical compound down by

heating.Answer

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A: CO2

B: CaO

C: Ca2O3

D: CO2

CaO

What is the chemical symbol for calcium oxide?

Answer

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calcium hydroxide

A: cloudy oxide

B: calcium oxide

C: calcium hydroxide

D: calcium carbonate

What is the chemical name for limewater?

Answer

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A: CLi2

B: CaCO3

C: C4Ca

D: CaO

CaCO3

What is the chemical formula for limestone?

Answer

18