Casey Stribling
Lab Partner: Anne Quackenbush
December 3, 2012
Pre-Lab #10
Flame Test Lab
Abstract: When a metallic ion is given more energy than its quantized energy levels allow, it releases
electromagnetic radiation in the form of visible light. Metal solutions were heated over a flame to
observe any colors they produced. The experiment was a success and did not have any detrimental
errors. The unknowns tested could not be positively verified due to similarities of line spectrums. The
experiment provided a better understanding of the photoelectric effect and quantized energy.
Introduction: An atom is very complex. This experiment focusses on Bohr’s theory. Electrons surround
the nucleus in rings. These rings each have their own level of energy they contain. They are also referred
to as quantum levels. Quantum levels closer to the nucleus contain less energy than the levels further
out. The electrons orbit as pairs. Since lower quantum levels contain less energy, then there are more
atoms the father outward you go from the nucleus. If an atom is given enough energy, then it has
trouble holding it all in because it is all about attraction. If electrons energy is added to the atom, then
the electrons will go down an energy level.
When metallic ions are heated, they produce light. This is because when they are heated they
become excited and the electrons move energy levels. That change produces electromagnetic radiation
usually in the form of visible light. This experiment uses Ba2+, Cu2+, Li+, K+, Sr2+, Ca2+, Na+, and a few
unknowns.
Purpose: The purpose of this lab is to explain why metallic ions emit light when heated by conducting
tests of known ions and comparing them to unknowns.
Procedure: A well plate was obtained and labeled with the names of the solutions that were tested.
Then, a dropperful of each solution was placed into its determined well. After putting on latex gloves, a
beaker with approximately 10mL of 6.0 M HCL and a nichrome wire loop were obtained. Then the
burner was lit and placed on a low setting. Before each test, the nichrome wire was thoroughly cleaned.
To remove the foreign particles, the wire was rinsed with distilled water using the wash bottle, and then
dipped into the 6.0 M HCL solution. After that, it was placed in the flame for a few moments and the
color that was emitted was observed and recorded. The same color was seen after every cleaning of the
nichrome wire. Due to the fact that sodium produces such a strong color, it was tested last. The clean
wire was placed in a single solution, placed over the flame and observations were recorded. This was
done for all seven solutions.
Results: All solutions including the unknowns had a clear color except for the copper nitrate. It had a
blue color.
Substance
Color
Ba(NO3)2
-Yellow/Green x2 - Yellow x4 - Green/Yellow x3
Cu(NO3)2
-Blue/Green x2 - Green x7
LiNO3
-Magenta x3 - Pink x2 - Red x 3
KNO3
-Purple x3 - Light Blue x3 - Lavender x2 - Orange x1
NaCl
-Orange/Bright Orange x8
Ca(NO3)2
-Green/Magenta/Orange x1 - Orange x3 - Purple x3 - Pink x1
Sr(NO3)2
-Red/Orange x2 - Orange x4 - Red x1 - Pink x1
Unknown
Color
A
-Light Purple/Lavender x8 - Pink x1
B
-Orange x7 - Orange/Red x2
C
-Green x2 - Yellow/Green x4 - Yellow x2
Conclusion: The purpose of this experiment was to find out why metallic ions produce color when given
energy by heating them over a burner. This happens due to the atoms’ energy being quantized. Once it
is given more energy than it can take, the electrons jump to higher levels and release electromagnetic
radiation when they jump back down. This was done by dipping a nichrome wire loop into the metallic
solutions and then placing it over the burner to observe the colors. The purpose was accomplished
because each solution gave a visible color that was observed. There is a high level of certainty in these
results. The results matched the accepted colors for the most part, having a few outliers that have
explainable occurrences. The unknowns could not be positively identified because some of the
substances produced similar colors. The unknowns can be narrowed down to two or three different
metallic ions, but there is too much uncertainty to positively identify one or the other. However, in the
case of unknown C, it was narrowed down to either barium nitrate or copper nitrate. The unknown
liquid had a color that was clear. The copper is known to have a bluish color. Knowing this, copper was
ruled out and unknown C is believed to be barium nitrate. The colors seen were in the visible light part
of the electromagnetic spectrum. Specifically between 400 and 750nm.
Discussion: This experiment was successful, but as seen in the results there were a few outliers. The
outliers most likely were due to errors in procedure. The steps of cleaning the nichrome wire loop were
most likely not followed as carefully as they should have been. The HCL produces its own color when
heated over the flame. Residue from the prior experiments and the HCL can cause a faulty color reading.
The human eye can see only certain wavelengths known as visible light. Everybody has a slight variance
to the colors they associate with the light that goes into their eyes. Some people have trouble seeing
certain colors at all. This probably accounts for the different shades of colors as seen in the results such
as blue/light blue, orange/yellow, red/orange, purple/pink/lavender... Once the nichrome wire was
dipped into a solution, while it was being transported to the flame it may have dripped into some of the
other wells containing the other liquids. There is no proof that this happened, but it is still a possible
error. With the number of trials executed, it was clear what the outliers were. The slight variety of
different shades of colors was expected due to the anatomy of the human optical system. The errors did
not affect the overall results at all except for the outliers. This process can be used to test other items to
possibly determine what metallic ions are present. When a glass rod is heated it produces a yellow
flame. This indicates that it probably contains some barium nitrate based on the data collected in this
lab.
The energy of a photon of light is calculated using the equation
If lithium’s line spectrum has a wavelength of 670.8nm, then the energy can be calculated as follows:
First, the frequency must be found so we can use the equation we have to find energy.
Since the colors that are given off are due to energy being given to the atom, you could use many tactics
to get it to produce color. Heating it over a flame is only one answer. You could heat it over a stove top,
run an electric current through it, or maybe even put it in a microwave (although this method is not
advised for safety reasons). Metallic salts are used widely in the fireworks industry to produce the bright
colors we see. When the salts are heated, they produce the colors we all see, just like the flame test.
This experiment brought forth a better understanding on how the photoelectric effect and
quantized energy occurs. There are many real life applications for this. Signal flares, fireworks, night
vision goggles, certain types of TVs and even remote controls use this technology. This technology is also
used in the development of solar energy. That is a great example of the photoelectric effect. Solar
energy could become widely used in the next 10 years. Overall, this experiment was a success. It
brought understanding to how things function and provided a solid base to build on for future learning
of quantum mechanics and the photoelectric effect.