Flame Test Lab
Situation: Julius and Annette Benetti are worried about some abandoned, rusted barrels of
chemicals that their daughter found while playing in back of their home. The barrels have
begun to leak a thick liquid. Your job is to identify the substance. Early work has indicated a
dissolved metal compound. Many metals, such as lead, have been determined hazardous to
human health. Such compounds are often soluble in water and are therefore easily absorbed
into the body.
Background: After electrons of an atom absorb energy to move from their ground state to
an excited state, they will eventually fall back to the ground state. When they do this the
energy that they had absorbed will be emitted in the form of light. Because each atom has a
unique structure and arrangement of its electrons, each atom will emit a unique type of light.
This is how the chemical flame test works. The atoms are excited when they absorb energy
when placed into the flame. As they emit energy in the form of light, the color of the flame will
change. For many metals, these changes are easily visible. However, even a tiny speck of
another substance can interfere with identification of the true color of the flame test. It is
important to keep your equipment clean.
Problem: To determine what metal is contained in the barrels behind the Benettis' house,
you must first perform flame tests with a variety of different metal compounds. Then you will
perform a flame test with the sample from the site to see if it matches any of the substances
that you have used as standards.
Procedure:
Your teacher will instruct you on the proper procedure for lighting the Bunsen burner:
1. Test each of the known compounds by dipping the wire loop into it and then placing it in the
burner flame and observing the color. Record this in the data table.
2. The partner not performing the flame test should observe each flame test with the
spectroscope. Record the spectral lines observed in the data table. This will represent the
"atomic emission spectrum" for each metal ion.
Flame Test Lab
SAFETY:
1)
DATA:
Metal Ion
Name________________________ Hr___
2)
3)
Color of the Flame
Atomic Emission Spectrum
(using Spectroscope)
Calcium
________________
Potassium
________________
Lithium
________________
Strontium
________________
Barium
________________
Sodium
________________
Copper(II)
________________
Unknown
________________
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QUESTIONS and ANALYSIS: (Use complete sentence when not simply filling in a blank.)
1. Which metal ion do you think was in the liquid in the barrel (unknown)? ___________________
How did you decide?
2. In general, for all metal ions, how did the color of each flame compare to the colors seen in the
spectroscope? Explain.
3. A student performed flame tests on several unknowns and observed that the flames were all
shades of orange. What could be done to correctly identify the unknowns? You may assume that the
burner used for the flame tests was not contaminated.
4. What happens in an atom to cause the colors seen in the flame and spectroscope during a flame test?
Be specific and use the following terms:
electrons, light, emit, absorb, ground state, excited state, color, energy
5. During a flood, the labels on three bottles of chemicals were damaged. The bottles were originally
labeled to contain copper(II) nitrate, sodium carbonate, and barium sulfate. Explain how you could
easily identify and re-label the three bottles. Be specific.
6. Some stores sell fireplace crystals. When sprinkled on the fire, they turn the flames colors such as
orange, red, yellow, and green. What type of substances do you think the fireplace crystals contain?
Orange:___________________
Yellow: ______________________
Red: _____________________
Green: ______________________