lab.Report114
hsn7077
inv_19_rubric.doc114 RUBRIC Investigation 19: What Factors Affect the Intensity of Color?
General
· Report is due by beginning of next week’ class. Late lab reports will not be accepted.
· One hard copy of the report per group.
· Attach the contribution sheets to the end of the report.
Formatting (points can be deducted if these items are not followed)
· Title page with Investigation name, date, lab section, group members’ names, TA’s name.
· Must be written in third person, past tense, passive voice; no use of first person, and no contractions or slang. Uniform in spacing (double space) and fonts,
· Label each of the sections listed below, bold or underlined.
· Use proper grammar and spelling. Use superscripts and subscripts for chemical formulas and scientific notation. Remember to put a zero in front of the decimal point.
· Include all bibliographic entries of all reference material used.
Introduction (lpt)
· Brief description of the goal in this experiment
· Brief explanation of the spectroscopy technique to support the investigation and the related concepts: light, transmittance, concentration, Beer-Lambert’s law, etc.
· Brief description of the experimental plan used to achieve your goal.
Procedure (2pts)
· Provide a list of reagents/equipment made available in the lab that you used.
· Molarities of solutions must be listed correctly.
· Proper subscripts and physical states are very important.
· Provide a clear description (in a paragraph style) of the procedures used during the course of the experiment; include concentration/volumes of solutions. This should be detailed enough that another group could duplicate your work.
Results (6pts)
· For one dye color, plot the following functions of %T vs. concentration:
· % transmittance (y-axis) vs. concentration (x-axis)
·
(
)
2
%
T
vs. concentration·
T
%
100
vs. concentration·
T
%
vs. concentration·
÷
ø
ö
ç
è
æ
100
%
log
T
vs. concentration· Plot and discuss ALL the functions of % T vs. dye concentration that you calculated.
· For each plot, remember to:
· Label x-axis and y-axis (with units)
· Use appropriate software to find the straight-line trends (such as m, y-intercept)
· Include the R2 factor as a statistical measure of the best straight-line fit
· Show an example of the spreadsheet formulas
· Also write the best fit equation for each plot:
(
)
(
)
b
ion
concentrat
m
T
f
+
=
%
· For example, if the slope is 0.6 and y-intercept is 4.2 for the
T
%
vs. concentration plot, then the equation is:(
)
2
2
.
4
6
.
0
%
+
´
=
ion
concentrat
T
· Show one example of calculation of making diluted solutions from 100% original dye solution
· Use of proper units
· Include and discuss the percent transmittance, %T, (light vs. dye) in terms of wavelength (which wavelength is best for each dye solution? Why?)
Table 1. Percent Transmittance by Wavelength
|
Dye Color |
430 nm (Blue/Violet light) |
470 nm (Blue light) |
565 nm (Yellow light) |
635 nm (Red light) |
|
Color 1 e.g. Red |
|
|
|
|
|
Color 2 e.g. Green |
|
|
|
|
|
Color 3 e.g. Blue |
|
|
|
|
· Include a table of the original data: dye concentration vs. %T
Table 2. Percent Transmittance of the 10 Dilutions of the Red Food Coloring
|
Concentration |
Blank |
0.1 |
0.2 |
0.3 |
0.4 |
0.5 |
0.6 |
0.7 |
0.8 |
0.9 |
1 |
|
%T |
|
|
|
|
|
|
|
|
|
|
|
Discussion (3pts)
a. Which graph gives the best fit line, or the straightest line?
1. Does it match the equation of Beer-Lambert’s law?
2. Explain each term (and its units) of the Beer-Lambert’s equation
b. Discuss how wavelength affected the percent transmittance of dyes
c. Discuss possible limitations in the spectroscopy technique used in this investigation
Conclusion (2pt)
· Restate the goal of this experiment
· Summarize the factors that affect the intensity of color and how
· Summarize the straight-line plot that relates the function of %T vs. dye concentration. Describe the usefulness of having a straight-line plot how is this related to Beer-Lambert’s law.
Works Cited (1pt)
Reference the manual and other reputable sources using ACS format.
Beatriz I. Smith 2/24/15
