Flame Test Lab
Chemists began studying colored flames in the 18th century and soon used "flame tests"
to distinguish between some elements. Different elements produce different colored
flames when they are being burned. Although some of the flames you will be seeing will
appear similar in color, their light can be resolved (separated) with a prism into
distinctly different bands of colors on the electromagnetic spectrum (ROYGBIV). These
bands of colors are called atomic line spectra, and they are UNIQUE to each element.
Violet
indigo
green
yellow
orange
red
Niels Bohr studied the line spectrum for hydrogen, and wondered what the specific line
spectrum had to do with the structure of the atom. He postulated that an electron can
have only specific energy values in an atom, which are called energy levels. Bohr
believed that the energy levels for electrons were quantized, meaning that only certain,
specific energy levels were possible.
How does an electron move between energy levels? By gaining the right amount
of energy, an electron can move, or undergo a transition, from one energy level to the
next. We can explain the emission of the light by atoms to give the line spectrum like
this:
1. An electron in a high energy level (excited state) undergoes a transition to a low energy
level (ground state). The transition is instantaneous & complete.
2. In this process, the electron loses energy, which is emitted as a photon (a particle
which behaves like a wave)
3. The energy difference between the high energy level and the low energy level is
related to the frequency (color) of the emitted light.
4. The mathematical formula that relates the energy of a single photon to its frequency
is E = hf.
E = energy
h = Plank’s constant (6.626 X 10-34 Js)
f = frequency
5. If you know the frequency you can calculate the wave length by using the following
formula: c = λf
c= speed of light (3.0 x 108 m/s)
λ=wavelength
f=frequency
What do the street lamps, salt, and fireworks
have in common?
They all contain SODIUM which gives off a
unique ORANGE flame when heated.
You are going to find out what color FLAME six different known samples make. You will then
use your results to work out which metal is in the unknown sample.
Your first Job is to make sure that your flame test wire is CLEAN. Do this
by holding the metal loop in the hottest part of the Bunsen burner flame.
If it is clean there should be no change in the color of the flame when the metal
loop is put into the flame.
If the metal loop is NOT CLEAN, clean it by dipping it into the HCl solution
provided then holding it in the burner flame until there is no change in the color of the flame.
You should have different loops for each sample. DO NOT cross contaminate samples by using
different loops then the ones assigned to the sample.
Your next job is to do the flame tests. Dip the wire loop into one of the known
solutions. Then hold the metal loop in the hottest part of the Bunsen burner flame.
Make a note of the color in the FLAME TEST CHART.
Continue to test the other known solutions. Keep going until you have recorded the color of al
of the known solutions.
Repeat job 2 but use the unknown solution. Can you figure out what metal is in this
solution (don’t forget to record the sample # in your chart)
Your Lab Report should have all of the following items:
1. Names, Date and Period (3 pts.)
2. Title (3 pts.)
3. Purpose (3 pts.)
4. Pre-Lab Answers (18 pts)/ Answer in complete sentences
5. Table (20 pts.)
6. Post Lab Answers (50 pts)/ Answer in complete sentences
Pre-Lab Questions:
1. What happens to an electron when energy is added?
2. What is released when an electron loses energy?
3. What determines the frequency (color) of photons?
4. Calculate the energy of a photon that has a frequency of 4.3 x 1019 hertz
5. What is the wave length of this radiation?
6. What color does this radiation emit?
The Flame Test
Objective: To identify atoms in solutions using the colors they emit when heated
Safety:
1. Place only the wire loop in the flame.
2. Do not knock over the flame, reach over it, or clutter your lab area with paper
3. Wear goggles at all times.
4. Do not horse around.
Instructions for flame tests:
1. Find a station with a Bunsen burner, seven containers of chemicals, and a wire
loop.
2. Ignite your Bunsen burners with your clickers. (your teacher will help you)
3. Dip the wire in the solution and hold the wire loop over the flame and observe
the color
4. Once you have collected your data, test your unknown solution (write down the
number). Write down your results and go back to your seat.
Solution
Color of Flame
Which atom is it?
Strontium
Sr2+
Calcium
Ca2+
Lithium
Li+
Sodium
Na+
Copper
Cu2+
Potassium
K+
Unknown #
Post Lab Questions:
1. Why do atoms give off light energy when heated? (Use “electrons” somewhere in your
answer)
2. If one did not properly clean one’s wire, what could happen?
3. Guess why different atoms give off different colors of light?
4. Write the electron configuration and Lewis dot structures for all the elements tested except
copper.
5. Is the change observed in this lab a physical change or a chemical change? Explain.
6. Why do you think that we used the metal salts instead of the pure metals? (think about the
properties of the pure elements)
7) If the frequency of a red spectrum line is at 1.60 x 1014 Hz, how much energy does each
photon of this light have?
8) If the frequency of a violet spectrum line is at 2.50 x 1014 Hz, how much energy does each
photon of this light have?
9) Which color of light is lowest in energy? _______________ Which is highest?
________________
10) What is the frequency (ν) of light which has 8.33 x 10-22 joules?