Purpose
To illustrate the principles behind fireworks and how they relate to the Bohr Rutherford model of the atom.

Materials

• Potassium chlorate, KClO3
• Sucrose (ground sugar)
• Concentrated sulfuric acid, H2SO4 [18 M]
• Copper (II) chloride, CuCl2
• Strontium nitrate, Sr(NO3)2
• Iron powder, Fe
• Heavy wall combustion test tube
• Support stand with test tube clamp or beaker with sand
• Electronic balance
• 4 ea. 50 mL beakers
• 400 mL beaker

Safety

• Read the MSDS/WHMIS sheets for all chemicals before using them
• Never grind potassium chlorate, it may explode
• Adequate ventilation is required
• Wear chemical safety glasses
• Ensure combustion tube is clean and not cracked
• Place a safety shield between reaction and audience
• Ensure opening of test tube is not pointed at any one
• Stay several feet back after initiating reaction

Procedure

1. In a beaker prepare a mixture of potassium chlorate and ground sugar by mixing equal amounts of both chemicals. (~50 mL). Do not grind the mixture together.
2. Add 12 g of the potassium chlorate/sugar mixture to a beaker and set aside.
3. In another beaker add 10 g potassium chlorate/sugar mixture and mix in 2 g of copper(II) chloride and then set aside.
4. In another beaker add 9 g potassium chlorate/sugar mixture and mix in 3 g of strontium nitrate and then set aside.
5. In another beaker add 9 g potassium chlorate/sugar mixture and mix in 3 g of powdered iron.
6. Pour the contents of the beaker made in steps 2-5 one at a time into a heavy-wall combustion test tube.
7. Using a test tube clamp, attach the test tube to the support stand behind a safety shield. Alternatively, the test tube can be placed upright in a beaker containing sand behind a safety shield. In either case, be sure to point the tube away from the audience and have them well back.
8. Initiate the reaction by adding several drops of concentrated sulfuric acid.

Results

• A bright and smoky flame is produced upon the addition of the sulfuric acid.
• The color of the flame will change depending on the metal present in the layer.
• The addition of copper ions turns the white flame blue, strontium ions turns the flame red, and iron yields a yellow flame.

Follow-Up Teaching Notes

• Energy released by the oxidation of the sugar is absorbed by the metallic ions in the salts.
• The excited state of the metallic ion is short lived and as it returns to its ground state it releases a specific amount of energy (specific wavelengths of energy).

Connections
Atomic theory, redox reactions, combustion.

Extension

• By removing the oxidizing agent (KClO3 ) and the salts, a black pillar can be produced by mixing concentrated sulfuric acid and sugar.
• Place 400 mL beaker on a tray and fill it with 100 mL of ground sugar
• Add 50 mL of concentrated sulfuric acid and stir.
• This demonstration illustrates the dehydrating properties of sulfuric acid, the presence of carbon in an organic compound, and the effect of an oxidizing agent, KClO3 .

Disposal/Clean-up

• Collect all the solid material that has been ejected out of the test tube using dustpan and broom.
• All the solid waste can be disposed of as regular solid waste (Check local regulations before any disposal activity).

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