Chemistry A: Dilutions Lab
Procedure:
Using a permanent marker, label ten of the plastic white ice cube trays “1”
through “10” as shown below:
1. Fill two or three beakers or cups with distilled water. This water will be
used for cleaning the medicine droppers.
2. In the first section of the ice tray, add 10 drops of food coloring. This
represents a pure chemical or substance. For this lab we can say that the
pure food dye has a concentration of 1 million parts of food coloring per
million. Observe the color and intensity of the pure food dye solution.
3. Using a medicine dropper, take a sample of one drop of the pure food
coloring from section #1 and dispense it into section #2.
4. Rinse the medicine dropper to get rid of all food coloring.
5. Using the rinsed medicine dropper, add 9 drops of pure water to the ice
tray section #2 and stir the solution with a straw or stirrer. The pure food
dye is now diluted to 1/10 of the original (pure) concentration. What is the
concentration of solution #2 in parts-per-million (ppm) of food coloring?
What is the intensity of the color of the food dye in the diluted solution of
section #2.
6. Sample one (1) drop of solution from section #2 place it in section #3.
Rinse the dropper again.
7. Using a rinsed dropper, add 9 drops of pure water to section #3 and stir
thoroughly. What is the concentration of solution in section #3 in ppm?
Again, record the intensity of the color of the food dye in section #3.
8. Repeat this serial dilution procedure for the remaining sections #4 through
#10. Be sure to carefully rinse the medicine dropper between each use.
After each dilution, use the table to record the new concentration of food
coloring in the sections in units of ppm.
Ice Tray Section Number
Concentration of Food
Coloring in ppm
Color Intensity of Diluted
Food Coloring Solution
#1
#2
#3
#4
#5
#6
#7
#8
#9
#10
Discussion, Observations, and Questions
9. In which section is the color most intense? Why?
10. In which section is the color least intense? Why?
11. Are there any sections where the liquid is colorless? Is there any food
coloring in these sections? How do you know?
12. Section #1 contains food coloring with no water added. What is the
percent concentration of food coloring in section #1?