L.O: To know what limestone is and how it can be decomposed using heat

Limestone Marble Calcium carbonate Chalk Calcite Travertine Tufa Limeshell Coral Marl

Limestone is a sedimentary rock.

It comes from the shells of sea creatures or from solids formed in the oceans long ago.

It is mostly made of calcium carbonate - CaCO3.

It is an important raw material for both the chemical and the construction industries.

What do you predict? Look at the available equipment for a hint!

What do you think the word equation is?

1. Making quicklime from limestone

Heat a spatula of calcium carbonate in a test tube. Clamp the test tube above the bunsen and use a delivery tube connected to limewater to see if carbon dioxide is given off.

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Quicklime - the lime kilnQuicklime - the lime kiln

• Limestone is heated in huge ovens known as lime kilns.

• The calcium carbonate decomposes into calcium oxide (quicklime) and carbon dioxide.

• Quicklime is a vital ingredient of cement, concrete and of most types of glass.

CaCO3 CaO + CO2

Water can now be added. What would the word equation be now?

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Slaked limeSlaked lime

• If water is added to quicklime the calcium oxide changes into calcium hydroxide (slaked lime).

• Slaked lime is a vital ingredient of various building materials.

CaO + H2O Ca(OH)2

• A solution of calcium hydroxide (limewater) is also used to test for carbon dioxide gas (it goes cloudy).

Limestone Cycle experimentLimestone Cycle experiment

2. Turning quicklime into slaked limeTip the quicklime into a watch glass and add a few drops of

water. Test this substance with UI. If calcium hydroxide has been made (an alkali) the UI will go purple.

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The “Limestone Cycle”The “Limestone Cycle”Calcium Carbonate

(limestone)

Calcium Oxide

(lime or quicklime)

Calcium Hydroxide

(slaked lime)

Calcium Hydroxide solution

(limewater)

Step 1: heat

Step 2: add a little water

Step 3: add more water and

filter

Step 4: add CO2

CO2

CO2

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LimestoneLimestoneIf soil is too _____ crops will fail. Limestone can also be used as a neutralising agent. There are two reactions to know:

1) Firstly, a THERMAL _________________ reaction is used to break the calcium carbonate down into calcium oxide (quicklime) and _______ __________:

2) This is then “slaked” with water to produce calcium hydroxide (“_________ lime”):

Calcium hydroxide is alkaline and is used to ______ acidic soil.

Calcium carbonate calcium oxide + carbon dioxideHEAT

Calcium oxide + water calcium hydroxide

Words – slaked, acidic, neutralise, decomposition, carbon dioxide