Unit 39 Laboratory Activity: Flame Tests
Goal: Observe different colors produced by excited electrons when salts are heated.
Equipment and Materials:
- Ideally, nickel-chromium wire; realistically, about a dozen steel paper clips.
- Salts such as table salt, epsom salts, baking soda, sodium borate, alum, or other powder. If you have a chemistry kit with cupric sulfate, calcium chloride, calcium oxide (lime), or zinc sulfate, these will also work.
- Candle or alcohol burner.
- Waxed paper or shallow dish.
- Unbend the paper clips and use the pliers to make a tiny loop about 5 mm in diameter on one end.
- Clean the paper clips with water and isopropyl alcohol to eliminate skin oils.
- Place a small amount of powder (approx. 1/16th teaspoon) on the paper and add a drop of water to make a paste.
- Get as much of the paste on the wire loop as possible.
- Use the pliers to hold the straight end of the wire, and position the loop of wire in the flame.
- Observe and record the color of the flame as the paste burns.
- Clean your wire or use a new one and repeat the test for other chemicals.
- If you have borax, start with a clean wire and warm the loop end.
- Dip the warm wire loop in sodium borate (borax) and then heat the borate mass.
- Dip the warm bead in one of the other salts so that some sticks to the bead.
- Heat the bead and salt together.
- Let the bead cool and record the color of the bead and the name of the salt used.
Summarize your technique and indicate how you would use flame testing or borate bead testing for chemical analysis (to identify chemical compounds).
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