Name _________________________________________
Kaspriskie
CP Chemistry 2015-16
Flame Test Lab
INTRODUCTION: An electron that possesses excess energy is said to be in the excited state. When an
electron in an excited state returns to its ground state, it does so by emitting excess energy as photons of
electromagnetic radiation, including visible light. The energy states of electrons are discrete: this means they
are fixed, specific energies that never vary. Each type of atom (each element) has different, characteristic,
discrete energy states, which are different from the energy states of all other atoms.
When an excited atom emits energy, the energy is not emitted continuously. Atoms emit photons of
only certain specific energies, which correspond exactly in energy to the changes in energy between energy
levels within the atom. Because atoms emit photons of only specific energies, the wavelengths of these emitted
photons can be used to identify atoms.
When light reveals its different component colors, it is referred to as a spectrum. You may have seen
sunlight or light from a light bulb separated by a prism into a rainbow pattern called a continuous spectrum.
When light from an atom’s energized electrons passes through a prism, a bright line spectrum is produced.
These colored lines occur at certain intervals within the spectrum (specific wavelengths), which are
characteristic for each element. Line spectra, and more modern techniques, are used routinely to determine the
presence of certain elements in a sample. As an example, if a chemist believes that an unknown sample
contains iron, he or she can generate a bright line spectrum for iron, and then compare the spectrum of iron to
the spectrum of the unknown compound. If the characteristic lines for iron are present in the spectrum of the
unknown sample, the sample must contain iron. Similarly, if a chemist takes a solution containing specific
cations (metal ions), the color that becomes visible when the solution is heated in a flame can aid in identifying
an unknown sample.
You have observed the bright line spectra of several elements using diffraction grating glasses. The line
spectra of excited state elements was viewed utilizing discharge tubes. A gas discharge tube is a long, narrow
tube filled with particular gaseous elements. The tube is fitted with metal electrodes at each end. When a high
voltage is applied through the tube, the atoms within the tube absorb, then re-emit energy. This energy can be
viewed as visible light. The bright line spectrum of the element becomes visible while wearing diffraction
grating glasses.
PURPOSE: To observe the emission spectrum of various cations.
PROCEDURE
1. Light the burner at your lab table. Adjust the burner flame so that the hottest part of the flame is clearly
visible.
2. Remove the nichrome wire from the solution at your lab table.
3. Hold the tip of the wire in the hottest part of the flame. Record the color of light given off next to the name
of the cation in your observations table. Be very descriptive.
4. Return the nichrome wire to the solution beaker.
5. When the teacher says “switch” move to the next lab table and repeat the procedure.
Continue to do so until you have recorded colors for all seven known solutions.
6. After all groups have finished with the seven known solutions we will put them aside and repeat the
procedure for the six unknown solutions.
FLAME TEST OBSERVATIONS
SOLUTION
METAL ION
lithium chloride
Li+
potassium chloride
K+
copper (II) chloride
Cu2+
iron (III) chloride
Fe3+
calcium chloride
OR
barium chloride
Ca2+
OR
Ba2+
strontium chloride
Sr2+
sodium chloride
Na+
UNKNOWN # OBSERVATIONS
1
2
3
OBSERVATIONS
IDENTITY
CONCLUSION PARAGRAPH RUBRIC
Based on the Pogil activity, video we watched in class and the lab you performed in class, you need to write a
conclusion paragraph. The paragraph should tell what happens to the electron within the atom. It should also
describe how wavelength relates to the structure of the atom, explain the atomic emission spectrum and how
you could use a flame test to identify unknown elements. Use the rubric below while writing your paragraph.
TOPIC
POSSIBLE PTS
Define atomic emission spectrum and explain its
use
2
Describe photon and its function in the lab you
performed
2
Define ground state and how it relates to the electron
2
Define excited state and how it relates to the electron
2
Define quantum and how it relates to the electron
2
Define wavelength
1
Relate wavelength and color of light given off
2
Relate wavelength of light emitted to the structure
of the atom
2
Explain how the flame test can be used to identify an
unknown element
2
Correctly identify the unknown solutions in your lab
2
Submit observations chart and rubric with paragraph
1
Total
20
RECEIVED PTS
___________ / 20