Name: _____________________ Lab Day/Time: _____________________ Lab Group Number: ____________________ CHM 114 Prelab Activity for Week 7 Investigation 19: ?What Factors Affect the Intensity of Color?? 2 Points Read Investigation 19 in your lab manual (3rd edition) and read Appendix B. Absorption spectroscopy is a technique that analyzes the light absorbed by a substance or solution. Absorption of light by a substance occurs as electrons are promoted to higher energy levels (opposite of emission spectroscopy). Substances that are colored (like the red paint on a bike) absorb specific wavelengths of light from sunlight or room light. The color we see is the net affect of the colors that are reflected back at us. A white or colorless substance (like chalk) does not absorb any visible light (but is likely absorbing ultraviolet and/or infrared light). A black substance (like coal) absorbs many different wavelengths of visible light, reflecting little or none. Would you expect a red-colored substance (such as red paint) to absorb red light? __________ Explain. Before collecting data for this experiment, you must calibrate your spectrophotometer (also called a colorimeter, not to be confused with a calorimeter). How will you prepare (or what will you use) for the calibration points? 0% transmittance point 100% transmittance point How often during your experiment do you have to calibrate your calorimeter? Do you have to recalibrate after you change the wavelength of light? Describe how you would prepare 20.0 mL of a solution that is 80% the concentration of the original solution? Write a short proposal describing how you plan to start the experiment.
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