1. Dilutions An Introduction

2. Activity overview In this activity you will visualize what is meant by a ‘dilution’. You will also examine how to express the dilution that has been made.

3. Part I: Dilutions made with food coloring

9. The intensity of the blue color decreases because, as we progress through the tubes in the series, the concentration of the blue food coloring in the tube decreases…. Let’s determine what dilutions of food coloring were made in each tube….

10. Determination of dilutions Dilution # Volume blue f.c. (mL) Total Volume (mL) Dilution (fraction) 15105/10 =1/2 25155/15 = 1/3 32102/10 = 1/5 41101/10

11. The dilution made in each tube is expressed by the following ratio: Volume of blue food coloring stock Total volume of dilution* *The total volume = Volume blue FC stock + Volume water

13. Part II: Dilution simulation with beads

14. Overview In this part of the activity, you will visualize dilutions by using colored beads as your red food coloring stock and clear beads as water. You will also observe how the dilution made correlates with the concentration of the dilution…

15. Determination of the concentration of your red bead stock… For your simulated red bead stock, concentration is defined as: # red beads volume of red beads

20. Let’s determine what dilutions of red bead stock were made in each tube….

21. Determination of dilutions Dilution # Vol red bead stock (mL) Total Volume (mL) Dilution (fraction) A153015/30 =1/2 B5255/25 = 1/5

23. Determination of concentrations of dilutions A and B The concentration of each dilution can be determined by physically counting the number of red beads in each tube. Concentration is simply: # red beads Total dilution volume Dilution# red beads Total volume of dilution (mL) Concentration (red beads/mL) A17903060 B62025