1. What’s in the water? Colorimetry and conductivity of solutions
Presenter: Part 2

2. Investigation 13C: Colored Solutions Chapter 13
How does the light that is absorbed into the solution related to the
color of the solution?

3. Think About It
Describe each of the colors of light as it is shined on the crystals below.
Why is the blue light the only light that is reflected?
What happened to the red and/or green light?

4. Safety Considerations
Follow these important safety precautions in addition to your regular classroom procedures.
Wear safety goggles at all times.
Lab Preparation
The solutions are made by putting one drop of food coloring per 100ml of water. However, the yellow solution needs two drops per 100 mL.
If the colored solution is reading an absorbance of greater than 1.5, the color is too dark and should be diluted with some more water.

5. What You Will Need
Device with SPARKvue software / Colorimeter / Cuvettes (5)
Food Coloring (red, green, blue, yellow) / Wash bottle with distilled water
Test tube rack / Test tubes, 20 mm x 150 mm (5)
Need pic of heater stirrer

6. Connecting a Sensor
Turn on the colorimeter sensor and then connect it using Bluetooth.

7. Open the Lab File
Open the 13C Colored Solutions lab file in SPARKvue under Experiments > Essential Chemistry.

8. Procedure Put 1 drop of each food coloring in each test tube.
Add 10 mL of water to each test tube and mix.
Using the pipette, take 3 mL of each solution and put it in the cuvettes. You should have four cuvettes, each with a different color.
Place 3 mL of water in the fifth cuvette. This cuvette will be used as a reference in your measurements.

9. Procedure
Wipe off the sides of the cuvette with solution and water. Only handle it by the top, then close the lid.
Calibrate the colorimeter with the distilled water (the water sample is called a “blank”).
10. Start data collection.

10. Procedure
11. Record the % Transmittance and absorbance at each available wavelength.

11. Procedure
12. Stop collecting data.

12. Analysis Soluti ons Red light Green light Blue light Orange light
660 nm
565 nm
468 nm
610 nm %T A
water
Red
Green
Blue
Yellow

13. Analysis Soluti ons Red light Green light Blue light Orange light
660 nm
565 nm
468 nm
610 nm %T A
water
100
0.00
Red
92.8
0.032
75.3
0.123
30.0
0.523
89.4
0.049
Green
27.5
0.561
36.9
0.433
33.7
0.473
7.1
1.150
Blue
19.8
0.704
21.6
0.666
72.3
0.141
3.1
1.502
Yellow
99.3
0.003
99.2
31.7
0.499
99.0
0004

14. Questions
If a solution has a high transmittance for a certain color of light, what does that mean in terms of photons of light interacting with electrons in the solution? Use specific evidence from the Data Table to justify your answer.

15. Questions
If a solution has a high transmittance for a certain color of light, what does that mean in terms of photons of light interacting with electrons in the solution? Use specific evidence from the Data Table to justify your answer.
If the light goes through the solution, the photons are not interacting. One example could be the Red solution with a transmittance of 92.8.

16. Questions
When a solution has a high transmittance for a certain color of light, does it also have a high absorbance for that color? Use specific evidence from the Data Table to justify your answer.
3. State the color of the solution which absorbed the most
a) green light b) blue light c) red light

17. Questions
When a solution has a high transmittance for a certain color of light, does it also have a high absorbance for that color? Use specific evidence from the Data Table to justify your answer.
No. When the transmittance of light for a certain color is high the absorbance is very low. One example could be the red solution with an absorbance of
3. State the color of the solution which absorbed the most
a) green light b) blue light c) red light

18. Questions
When a solution has a high transmittance for a certain color of light, does it also have a high absorbance for that color? Use specific evidence from the Data Table to justify your answer.
No. When the transmittance of light for a certain color is high the absorbance is very low. One example could be the red solution with an absorbance of
3. State the color of the solution which absorbed the most
a) green light b) blue light c) red light
red

19. Questions
When a solution has a high transmittance for a certain color of light, does it also have a high absorbance for that color? Use specific evidence from the Data Table to justify your answer.
No. When the transmittance of light for a certain color is high the absorbance is very low. One example could be the red solution with an absorbance of
3. State the color of the solution which absorbed the most
a) green light b) blue light c) red light
red orange/yellow

20. Questions
When a solution has a high transmittance for a certain color of light, does it also have a high absorbance for that color? Use specific evidence from the Data Table to justify your answer.
No. When the transmittance of light for a certain color is high the absorbance is very low. One example could be the red solution with an absorbance of
3. State the color of the solution which absorbed the most
a) green light b) blue light c) red light
red orange/yellow green

21. Questions
Do the dye molecules in food color absorb a single color of light or a range of colors? How do you know?
When light matches the color of the solution, is it mostly transmitted or absorbed? Justify your answer with data.

22. Questions
Do the dye molecules in food color absorb a single color of light or a range of colors? How do you know?
A range of colors. This is evident from the different shades of color that can exist.
When light matches the color of the solution, is it mostly transmitted or absorbed? Justify your answer with data.

23. Questions
Do the dye molecules in food color absorb a single color of light or a range of colors? How do you know?
A range of colors. This is evident from the different shades of color that can exist.
When light matches the color of the solution, is it mostly transmitted or absorbed? Justify your answer with data.
The light that matches the color of the solution is mostly transmitted. For example, the red solution mostly transmitted red light.

24. Questions
Consider the color wheel below. Red and green are considered complementary colors, as are violet and yellow. When light is shone through a solution that is a complementary color to that of the solution, is it mostly transmitted or absorbed? Justify your answer with data.

25. Questions
Consider the color wheel below. Red and green are considered complementary colors, as are violet and yellow. When light is shone through a solution that is a complementary color to that of the solution, is it mostly transmitted or absorbed? Justify your answer with data.
The complementary color has the highest absorbance. This is most evident in the blue solution since it mostly absorbed the complimentary orange color.

26. Questions
What does the absorbance of red, green and blue tell us about the way the yellow color in our experiment is made? 


27. Questions
What does the absorbance of red, green and blue tell us about the way the yellow color in our experiment is made? 

For the yellow the most absorbed color is blue. The other colors are highly transmitted.

28. Questions
Research the way color books and magazines are printed. Explain the acronym CMYK. Why do printers use CMYK color instead of RGB? 


29. Questions
Research the way color books and magazines are printed. Explain the acronym CMYK. Why do printers use CMYK color instead of RGB?

In the printing press days, to achieve color, each ink (cyan, magenta, yellow, and black) had its own plate. First the printer would lay down one color, wait for it to dry, lay down another color, and wait for it to dry and so on. Printing presses still work on that same theory to this day with the exception that offset printers can use a “spot” color which can be added to achieve a specific color (usually a Pantone color). As the printing age has progressed, the digital printer has come a long way, allowing printing in RGB as well.

30. Questions? loschiavo@pasco.com