FLAME TEST LAB
PROBLEM: How can the identity of an unknown metal be determined?
BACKGROUND INFORMATION:
When atoms are placed into a flame, electrons absorb energy. This extra energy causes the
electrons to jump into an excited energy state, also known as a quantum jump. Because
energy must always be conserved, electrons re-emit this energy as a photon when they
return to their ground state. The amount of energy in the photon (particle of light)
determines its color. The order of energy follows the visible light spectrum with red being
the lowest and violet being the highest (red, orange, yellow, green, blue, indigo, and violet)
The arrangements of electrons (electron configuration) determine the sizes of the quantum
jumps. Remember, quantum jumps are measured by viewing the spectrum of color emitted
by the photon when the electrons return to their ground state. When viewed with the
naked eye, the spectrum will appear all one color. However, we can separate out the light
into its spectrum using a spectroscope. This spectrum helps us determine which element is
present.
In this lab, we will record the flame color test for various metals by soaking a wood splint in
water, adding the salts to the splints and putting the salt and splint into a flame. Finally we
will use the data to try to identify a metal in an unknown salt solution.
HYPOTHESIS: _______________________________________________________________________________
PRE-LAB
1. Write the electron configurations for the following elements

Sodium _________________________________________________________

Calcium _________________________________________________________

Lithium _________________________________________________________

Strontium _______________________________________________________

Potassium _______________________________________________________

Copper __________________________________________________________

Chlorine _________________________________________________________

Sulfur ___________________________________________________________

Nitrogen ________________________________________________________

Oxygen _______________________________________________________
2. Explain Conservation of Energy.
MATERIALS:





Metal salt solutions (CaCl2, CuCl2, LiCl, KCl, SrCl2-6H20, NaCl, Unknown)
Bunsen Burner
7 wooden sticks (soaked in water)
100 mL water
7 weighing boats
PROCEDURE:
1. Fill 100 mL beaker half full with water. Place the 7 wooden sticks in the water to
continue to soak.
2. Fill a second 100 mL beaker with water, label this “rinse water”
3. Label 7 weighing boats Ca, Cu, Li, Na, K, Sr and unknown. Place one scoopful (about
0.5 g) of each solid metal chloride into corresponding weighing boats
4. Light the Bunsen burner, adjust until flame is blue.
5. Dip the soaked end of wooden stick into one of the metals. Place in to flame and
observe color. Be careful not to drop any of the salt into the barrel of the Bunsen
burner, as it will give you a large degree of error.
6. Extinguish flame by placing wooden stick in “rinse water” beaker.
7. Record observations in data table
8. Repeat with the other metals
9. Follow steps 5-7 to test the unknown and use the data from the prior metal
solutions to try to hypothesize what the unknown metal is
10. Clean up station. Throw left over salts and sticks in the trash. Flush rinse water
down the sink. Wash and dry equipment. Wipe down station.
DATA:
Sample
CaCl2
Calcium chloride
CuCl2
Copper(II) chloride
LiCl
Lithium chloride
KCl
Potassium chloride
SrCl2
Strontium chloride
NaCl
Sodium chloride
Unknown
Table 1.1
Metal
Flame color
*Wavelength values here are given for the
mid-range of the color indicated.
ANALYSIS
Table 1.1
Sample
Metal/
cation
Flame
color
Wavelength
(nm)
𝒉𝒄
𝝀
1m=10-9nm
𝑬=
Wavelength
(m)
Energy (J)
CaCl2
Calcium
chloride
CuCl2
Copper(II)
chloride
LiCl
Lithium
chloride
KCl
Potassium
chloride
SrCl2
Strontium
chloride
NaCl
Sodium
chloride
Unknown
1. Based off the color you observed, use Table 1.1 to record your wavelength in
nanometers (nm).
2. Convert your wavelength from nanometers (nm) to meters (m) and record in the
data table above. Show your work for at least one conversion.
3. Using the wavelength in meters, calculate the Energy in Joules (J) using the
following equation and constants (show your work).
𝒉𝒄
𝑬=
h= 6.63x10-34Js c=3.00x108 m/s
𝝀
4. Explain what is happening to the electrons at the atomic level? Make sure to include
what excites the electrons and how the different colors of light are produced.
5. What was your unknown? Explain how you reached this conclusion.
Reflection: Write a paragraph discussing the lab: what worked, what didn’t work, what
you learned and how this lab relates to the material discussed in class.
Category
Procedure
Data/
observations
Analysis
Reflection
Lab Rubric
Description
Did you answer your pre-lab questions? Did you
follow procedures correctly? Did you adhere to
all safety protocol? Did you wear your apron and
goggles? Did you clean up and dispose of
chemicals properly?
Did you record your data accurately? Do you have
a table to display your data?
Do you understand what you observed? Can you
draw a conclusion? Are your analysis values
visible? Do you show proper significant digits and
unit of measurements? Did you quantify your
calculations correctly?
Did you use complete sentences? Are there at
least 5 sentences? Did you mention your possible
reasons for error? Did you mention what you did
well? Could improve on? Did you say what you
learned?
Total (30 pts)
20% (6 pts)
15% (4 pts)
45% (14 pts)
20% (6 pts)
Your score