Flame Test Lab
Name __________________________________
Date ______________ Period _______________
Introduction:
As electrons absorb energy, they jump to a higher energy level called an excited state. Electrons
in excited states are not stable and to become more stable they fall to lower energy levels. When they fall,
they release energy in the form of electromagnetic radiation. If the wavelength, λ, of the released photon
is between 400 and 700 nm, the energy is emitted as visible light. The color of the light depends on the
specific energy change that is taking place.
White light is a continuous spectrum in which all wavelengths of visible light are present. An
excited atom, however, produces one or more specific lines in its spectrum, corresponding to the specific
changes in energy levels of its electrons. Every metallic ion will produce the same emission line spectrum
regardless of the salt used because each metal has a distinct electron configuration. When using a
spectroscope, one can differentiate the colors emitted when that element is excited. However, with the
naked eye, only a blend of the line colors will be visible.
Flame tests are a quick method of producing the characteristic colors of metallic ions (the element
written first in the compound). The loosely-held electrons of a metal are easily excited in the flame of a
lab burner. The emission of energy in the visible portion of the spectrum as those electrons return to
lower energy levels produces a colored flame. The color is a combination (blending) of wavelengths of
each transition, and may be used to determine the identity of the ion.
In this investigation you will perform flame tests on different salts which contain 7 different
metallic ions. Metals will produce the same color in a flame test regardless of the salt used because a
particular metal ion always has the same electron configuration so electrons jump to an excited state and
fall back to a lower level in the same pattern every time they are heated.
Fireworks use different salts as the source of color. Metallic ions are excited by the energy of the
explosion. As the electrons lose energy (fall to a lower energy level) they produce colors exactly like the
flame tests.
Pre-Lab Questions: Read the entire lab and answer the following questions before doing the experiment.
1. Write out the electron configuration for each of the metallic ions to be tested in this investigation.
Ba+2 _____________________________________________________________________
Cu+2 _____________________________________________________________________
Li+1 _____________________________________________________________________
K+1 _____________________________________________________________________
Sr+2 _____________________________________________________________________
Ca+2 _____________________________________________________________________
Na+1 _____________________________________________________________________
2. What wavelengths correspond to the visible spectrum? ______________________________________
Which color has the shortest wavelength? ________________ The longest? _________________
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3. The metal salts will be (heated/ electrocuted) by a flame and (jump up/fall down) to a (higher/lower)
energy level. Because the excited electrons are unstable, they immediately (jump up/ fall down) to a
(higher/lower) energy level (releasing/absorbing) energy producing different colors.
4. Explain why a metallic ion produces a characteristic color in a flame test, regardless of the compound
used as the source of the ion? ___________________________________________________________
Materials:
cotton swabs
unknown salt
BaCl2
CuCl2
crucible tongs
Ba(NO3)2
Cu(NO3)2
NaNO3
Ca(NO3)2
NaCl
LiNO3
KCl
CaCl2
Sr(NO3)2
KNO3
SrCl2
Procedure:
1. Put on goggles and an apron. Tie back loose hair. Put your book bags on your chair as the lab
will be completed in the dark. This lab will be performed moving from station to station.
Each station has a salt solution in labeled beakers, a Bunsen burner, crucible tongs and a
supply of cotton swabs. One station will have an unknown salt solution.
2. Make sure the burner is lit and has a blue or almost clear flame. With your tongs, pick up the
end of a swab and soak the cotton end in the solution. Hold the soaked-end of the swab in the
clear part of the flame and record the flame color in the Data Table. Eventually the swab will
burn giving a characteristic yellow color. Do not write yellow for each solution! Be sure you
are recording the solution’s flame color. Placed the used swab in the waste beaker.
3. Possible colors: yellow, orange, yellow-green, green (blue-green), red and lilac (peach)
4. When all groups have completed their observations, the class will be instructed to clean up the
lab area. Wash your hands before leaving the lab.
Data Table:
Salt Solution
Color
Salt Solution
Ba(NO3)2
KNO3
BaCl2
KCl
Cu(NO3)2
NaNO3
CuCl2
NaCl
Sr(NO3)2
Ca(NO3)2
SrCl2
CaCl2
LiNO3
X(SO4)
Color
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Questions:
1. When electrons of metallic ions are heated they move to a ________________ energy level or a(n)
________________ state. When the electrons “fall” back to a _________________ energy level they
_______________ energy in the ___________________ portion of the spectrum.
2. The colors seen when the metal salts are burned represent a _______________________ of all the
lines that each ion produces when the electrons are excited and return to the ground state.
3. According to your data, determine the characteristic color produced when the following metals are
excited:
a. lithium ______________________
e. sodium _______________________
b. strontium ____________________
f. barium _______________________
c. calcium _____________________
g. copper _______________________
d. potassium____________________
h. unknown _____________________
4. When a glass rod is heated, a yellow flame is observed around the point of heating. What does this
mean the glass is made of? _________________Why is it observed when glass is heated?
__________________________________________________________________________
5. How do you think metallic salts are used in fireworks?
__________________________________________________________________________
__________________________________________________________________________
6. Explain why a metallic ion produces a characteristic color in a flame test, regardless of the compound
used as the source of the ion.
_________________________________________________________________________
_________________________________________________________________________
7. What color did the unknown metal salt burn? _______________
8. What metal is in the unknown compound? _________________
9. Based on your results and observations, would this method be practical to determine metals in a
mixture? Explain.
__________________________________________________________________________
__________________________________________________________________________
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