PACT Due Dates

Jeremiah Brooks - Flame Test Lab

Flame Test Lab

California State Content Standard

Atomic and Molecular Structure 

1. The periodic table displays the elements in increasing atomic number and shows how periodicity of the physical and chemical properties of the elements relates to atomic structure. As a basis for understanding this concept: 

j.   Students know that spectral lines are the result of transitions of electrons between energy levels and that these lines correspond to photons with a frequency related to the energy spacing between levels by using Planck’s relationship.

Principles Investigated  

           According to the Bohr model of the atom, electrons may only occupy certain energy levels.  When an atom absorbs energy, electrons can jump to higher energy levels.  Since the atom is unstable at this higher energy level, the atom releases the excess energy in the form of a photon of light.  The release of the photon allows the excited electron to return to the “ground state.”

            Visible light is a continuous spectrum where we can see all colors of light.  An excited atom will only produce one or more specific wavelengths of light in the form of a photon.  Since each atom has different numbers of electrons and various ground states, different atoms will produce different photons of light.

            A flame test is a qualitative method of determining the identity of metallic ions.  The loosely held electrons of metals allow them to be easily excited by the energy produced from the flame of a Bunsen burner.  The combined colors of the released photons of light cause each ion to produce a flame with a special color.  This color is characteristic for that particular metal ion.

  Materials

  • Bunsen burner
  • Q-tips
  • 2-250mL Beakers
  • Distilled Water
  • 9-100mL Beakers
  • Barium Nitrate
  • Calcium Nitrate
  • Copper (II)  Nitrate
  • Lithium Nitrate
  • Potassium Nitrate
  • Sodium Chloride
  • Strontium Nitrate
  • Unknown #1
  • Unknown #2

  Safety 

     1.    .Always wear your goggles and apron.

            2.    Since you are dealing with open flame, do not wear loose clothing and tie back all long hair.

            3.    Some of the salts are toxic.  If you come in contact with one of the salts, wash the effected area                  thoroughly.                                                                                    

  Procedure 

            1.     Turn on the Bunsen burner when instructed by your professor.

            2.    Place one Q-tip in each of the 7 unknown solutions.

            3.    Let each Q-tip soak for at least 2 minutes.

            4.    Make sure the Q-tip is thoroughly moist.  Place the moist end of the Q-tip into the open flame near the     Bunsen burner. 

            5.    Make careful observations of the resulting flame color.

            6.    Repeat steps 2-5 for each of the unknown solutions.

            7.    Turn off the Bunsen burner.

  Clean Up

            1.     Place the Q-tips in the appropriate waste container located at each lab station.

            2.    Clean your lab table.

            3.    Wash your hands.

    Questions 

            1.     Why does each of the metallic ions heated in this experiment release photons of light?                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       

            2.    Why is the flame color different for each metallic ion?                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       

            3.    Based on your observations which metallic ion was present in Unknown #1? Explain?                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           

            4.    Based on your observations which metallic ion was present in Unknown #2? Explain?                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           

            5.    Draw an energy level diagram depicting how light was produced by heating each metallic ion.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               

            6.    Put the metallic ions in order of increasing wavelength of light emitted.





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Norman Herr,
May 5, 2011, 12:33 AM
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