Download Flame Test Lab - Mrs. Sue Ellen Beek

Flame Test Lab
Learning Target 2: I can distinguish between an excited and ground state atom and use this to explain
flame tests, quantized energies of electrons, and chemiluminescence. (Objectives 7-10)
Background: When a metallic element is heated in a flame, the metal’s electrons absorb energy from the
flame. This absorbed energy (quantum) allows the electrons to be promoted to excited energy levels
“quantum jump.” From these excited energy levels, the electrons naturally want to make a transition, or
relax, back down to the ground state. When an electron makes a transition from a higher energy level to a
lower energy level, a particle of light called a photon is emitted. The amount of energy in a photon
determines its color, with red being the lowest energy and violet corresponding to the highest energy.
Photons outside the visible spectrum may be emitted, but we can’t see them. The exact energy of the
emitted photon, and its corresponding wavelength and color are unique to each metallic element. As a
result, the color observed when a metallic element is heated in a flame can be used as a means of
identification.
Title: The effect of using a flame test to identify the color and symbol of known metal ions, an unknown
metal ion and a mixture of metal ions.
Purpose:
1) to observe the different colors emitted by metal ions in a flame test
2) to predict the identity of an unknown metal ion using a flame test
3) to learn why cobalt glass is useful in flame tests
Hypothesis: If I burn different salt solutions, they will have the same/different colored flames.
Materials:
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Salt solutions (barium, calcium,
lithium, potassium, sodium,
strontium, copper)
Unknown metal ion solution
Mixture of potassium and
sodium ions
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Bunsen Burner
Matches
Goggles and Apron
Wooden Splints
Cobalt Glass
Data and Calculations:
The effect of the type of salt solution on the color of the f lame.
Metal Ion
Ba+2
Ca+2
Li+
K+
Na+
Sr+2
Cu+2
Formula of Salt
BaCl2
CaCl2
LiCl
KCl
NaCl
SrCl2
CuCl2
Color of Flame
The effect of using a flame test to identify an unknown metal ion.
Color of Flame: _________________
Symbol and Charge (i.e. Cu+2): _______________
The effect of using a flame test to identify mixture of metal ions.
Color of Dominant Ion: __________
Color of Recessive Ion: __________
Symbol of Dominant Ion: __________
Symbol of Recessive Ion: __________
Analysis Questions:
1.
2.
3.
4.
Can a flame test be used to identify a metal ion? Why, or why not?
In your opinion, which element tested gave the most intense color?
What is the purpose of using the cobalt glass in the flame test?
The energy of colored light increases in the order of red, orange, yellow, green,
blue, indigo and violet. List the metallic elements used in the flame test in
increasing order of energy of light emitted. For example, K+ should be last
because its true color is a lavender (purple).
5. During a flood, the labels from three bottles of chemicals floated away. The
unlabeled bottles of white solids were known to contain the following solutions:
strontium chloride (SrCl2), ammonium chloride (NH4Cl), and potassium chloride
(KCl). Explain in detail how you could use flame tests to easily relabel the bottles
correctly indicating what colors you would expect to see.
6. Betty Lou is suing Acme Chemical Company for 4 million dollars. She claims she
saw a bright green flash of light at the time of an explosion on the evening of
10/23/08 as she was driving by the Acme site and was exposed to unsafe
conditions. Acme chemical company stores potassium chloride in large tanks at
their site and claims nothing happened on the stated evening. Write a paragraph
defending either Betty Lou or the Acme Chemical Company in this lawsuit.
7. How could you determine if copper were in your drinking water.
Summary:
In your summary, explain the all purposes of your experiment. Restate your
hypothesis and explain whether it was accepted or rejected. Describe what information and
skills you learned and future applications to real life.
Sign and Date:
Safety
1) Wear safety goggles and a lab apron.
2) Long hair and loose clothing should be confined.
3) Consider all salt solutions toxic by ingestion; avoid contact with eyes,
skin and mucous membrane. Be sure to thoroughly wash hands when
finished with the experiment.
Procedure:
1. First, light a match. Second, turn on your Bunsen burner. Hold the match
over the top of the burner. You may need to adjust the air vent on the
burner to get a blue cone. A yellow color flame means too much gas, not
enough air. If the flame keeps blowing out, reduce gas flow.
2. Take a wooden splint out of the first salt solution to be tested. (You may
only use one wooden stick from each solution!) Hold over the tip of the
blue cone and record the color of the flame produced in the data table.
Place the wooden splint on the wire mesh. Repeat this for all the salt
solutions.
3. Test the color of the flame produced by the unknown and record with
ion is present (i.e., Na+, Ca+2, etc)
4. The beaker labeled “M” contains K+ and Na+ ions. Test the color of the
flame produced by the mixture. With your naked eye, identify the color
and symbol of the dominant ion. Then, look through the cobalt glass to
identify the color and symbol of the recessive ion. The purpose of the
cobalt glass is to filter out the dominant color in a mixture of two ions.
Record the colors and symbols of the ions. (HINT! You should see both
K+and Na+in the flame.)
5. When finished, take all wooden splints and rinse them thoroughly with
water before disposing in the trashcan.