Flame Tests Labs

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					                        Flame Tests Lab

                        Name ________________________                     Period _____

Problem: Can elements be identified by using a flame test?

Background Information: What do street lamps, salt, and fireworks have in common? They all contain Sodium, which
gives off a unique orange flame when heated. Every atom consists of a nucleus with tiny electrons whizzing round it. The further
away from the nucleus they are, the more energy the electrons have. If a metal atom is heated, the electrons get enough energy to jump
higher away from the nucleus. When they fall back closer to the nucleus, they give off this extra energy as light.

Different metals produce different colored light. If we look at the color of the light made when a
solution of metal is heated in a flame, we can tell which metal is there. By placing atoms of a
metal into a flame, electrons can be induced to absorb energy and jump to an excited energy
state, a quantum jump. They then return to their ground state by emitting a photon of light (the
law of conservation of energy indicates that the photon emitted will contain the same amount of
energy as that absorbed in the quantum jump).

The amount of energy in the photon determines its color; red has the lowest energy in the
spectrum of visible light, energy increases through the rainbow of colors from orange,
yellow, green, blue, indigo, and finally violet having the highest energy visible light
spectrum. Photons outside the visible spectrum may also be emitted, but we cannot see them. The energy of the emitted photon
determines the color of light observed in the flame. The flame color may be described in terms of its wavelength. Visible light is a
form of electromagnetic radiation. Other familiar forms of electromagnetic radiation include y-rays, X-rays, ultraviolet (UV)
radiation, infrared (IR) radiation, microwave radiation, and radio waves. Together, all forms of electromagnetic radiation make up the
electromagnetic spectrum.

Purpose: In this lab we will record the flame test color of several metals by using a soaked wooden splint of salts, or ionic
compounds of those metals then placing the splint into a Bunsen burner flame. The human eye sees yellow very well, since it is in the
middle of the spectrum visible to the eye. Colors at the edges of the visible spectrum, especially violet, are more difficult to see.

Experiment Overview:
Pre-Lab Questions
    1. Fill in the blanks: When an atom absorbs energy, the electrons move from their ___________ state to an ______________
       state. When an atom emits energy, the electrons move from a(n) __________________state to their ____________ state and
       give off _______________.

    2.   Is a flame test a qualitative test or quantative test for the identity of an unknown? Explain.


              Safety goggles                                8 Metal Ions:
              Bunsen burner

                                                                 LiCl         SrCl2     NaCl
                                                                 KCl          BaCl2
                                                                 CaCl2        CuCl2

         1.   Put on goggles.
         2.   Pass the wooden splint through the flame and observe the color of the flame. Record results in the data table of. DO
              NOT let the wooden splint burn.
         3.   Be careful NOT TO MIX the splints in the containers.
Results Data Table:
Metal Ion                                               Color of flame
Sodium chloride (NaCl)

Calcium chloride (CaCl2)

Strontium chloride (SrCl2)

Potassium chloride (KCl)

Lithium chloride(LiCl)
Copper (II) chloride (CuCl2)

Barium chloride (BaCl2)

Conclusion questions:

1.   Is the flame color a test for the metal or for the chloride in each compound? Explain.

2.   What color of light is lowest in energy? What is highest?

     Lowest-                                 Highest-

3.   The alkali metals cesium (Cs) and rubidium (Rb) were discovered based on their characteristic flame colors. Cesium is named
     after the sky and rubidium after the gem color. What colors of light do you think these metals give off when heated in a flame?
     Cesium-                                                  Rubidium-

Compound Name                        Formula                              Color
Sodium chloride                      NaCI                                 Orange
copper (II) nitrate                  Cu(NO3)2                             Green
copper (II) sulfate                  CuSO4                                Blue
iron (III) nitrate                   Fe(NO3)3                             Yellow
potassium chloride                   KCI                                  Purple
strontium nitrate                    Sr(NO3)2                             Red

4. A fireworks employee works in a lab that designs fireworks. He wants to create a firework display that burns blue, red, and orange.
If you were helping, what chemicals from the data above would you recommend?
         A. NaCI, CuSO4, and Fe(NO3)3
         B. CuSO4, KCI, and Fe(NO3)3
         C. KCI, CuSO4, and NaCI
         D. Sr(NO3)2, CuSO4, and NaCI
5. Suppose you were a firefighter and you were called to a chemical plant fire. Upon arrival you see a bright violet/purple flame.
Which chemical would that tell you is burning?
         A. Sodium Chloride
         B. Strontium Nitrate
         C. Iron Nitrate
         D. Potassium Chloride

6. If you observed another firework burn which started yellow and then turned blue, which two chemicals were used?

7. Explain 2 of the glass tubes by comparing the color of the tube to the color you see using the spectroscope.

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