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Senior Seminar: Science, Technology, And Society (STS190 HM)
Harvey Mudd College
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Honors Chemistry Name______________________________ Lab – Flame tests and emission spectra - Online PD_____ Date______________________
OBJECTIVES: 1. To identify the visible light spectrum and its relative energy values. 2. To identify an unknown substance based on laboratory data. 3. To explain the terms: energy level, electron, ground state, excited state and how these relate in Atomic theory to produce specific wavelengths of energy.
BACKGROUND : When an element is heated, a characteristic color of light is given off. In this investigation, you will research and explain why this occurs.
PROCEDURE :
- Watch the flame test demonstration: youtube/watch?v=1EXr_L7Ojqg&disable_polymer=true
- Record the color of each flame in the data table below.
- Watch this video and record the flame test color for unknown “C” youtube/watch?v=3hSmDnXJEGA
- Watch this video and record the flame test color for unknown “D” youtube/watch?v=chHUHW2TdKw
- Identify the "unknown" by comparing its color(s) to the known metal ions. It will be one of the known metal ions.
DATA TABLE : Tested element
Potassium Ion K+ (KCl)
Barium Ion Ba+ (BaCl 2 )
Calcium Ion Ca+ (CaCl 2 )
Strontium Ion Sr+ (SrCl 2 )
Lithium Ion Li+ (LiCl)
Sodium Ion Na+ (NaCl)
Copper Ion Cu+ (CuCl 2 )
UNKNOWN “C”
UNKNOWN “D”
Color of Flame
UNKNOWN ANALYSIS: Predict the composition of the "unknowns" from the list of knowns & state your supporting data.
Analysis: Clearly Label the following on the visible light spectrum below: MOST ENERGY, LEAST ENERGY, HIGHEST FREQUENCY, LOWEST FREQUENCY, HIGHEST (longest) WAVELENGTH, LOWEST (shortest) WAVELENGTH.
Explain why the same flame applying the same amount of energy input causes a different color of light to be released from different types of elements (as in your flame tests)? Describe this in terms of electron configurations and electron movements between energy levels. Remember what it means when we say spectra lines are like a fingerprint of an element.
Each of the compounds contained another ion, the chloride ion. How do we know that the color change that we see is a result of the metal ion and not the chloride ion?
Calculations: Fill in the Table Below ( be sure to show work with units for each calculation ).
- Calculate the frequency (in Hz) and wavelength (m) of electromagnetic radiation that would be released by each electron shift. You will need the formulas discussed earlier in the chapter to do this. 2. Using the frequency and wavelength, identify the type of light produced by each electron shift. If visible light is produced, then state which color of visible light would be observed. You will need to look at the Electromagnetic Spectrum Diagram in your note packet****. Remember 1m = 1x10 9 **nm.
- NOTE: The Electromagnetic Spectrum lists visible light as having a wavelength range of 400nm-700nm.**
What is this range in meters? 400 nm = ___________m 700 nm = _________________m
Energy level (high)
Energy level (low)
Energy Change ΔE (J)
Frequency (Hz or 1/sec)
Wavelength (m)
Type of Light Released
Color of visible light observed (if applicable) 1m=1x10 9 nm A. 2 1 1 x 10-
B. 3 2 3 x 10-
C. 5 2 4 x 10-
D. 4 3 1 x 10-
Work Space for calculations: A.
B.
C.
D.
History work beacuse bad
Course: Senior Seminar: Science, Technology, And Society (STS190 HM)
University: Harvey Mudd College
