2. Methods

Independent variables:
The independent variable is the different coloured skittles(Red, Green and Yellow).

Dependent variables:
The dependent variable is the Rf value measured from the chromatography paper.

Controlled variables:
(a)  Type of candy
(b)  Length of chromatography paper
(c)  Type of material used to draw the line on the chromatography paper.
(d)  Amount of dye
(e) Type of Solvent

2.1 Equipment List
  • Filter paper strips x 9
  • Conical Flask x 3
  • Red Skittles x 3
  • Yellow Skittles x 3
  • Green Skittles x 3
  • Red Food Colouring
  • Green Food Colouring
  • Yellow Food Colouring
  • Water
  • Ruler
  • Pencil
  • Petri Dish x 3
  • Wooden Ice-cream sticks x 3
  • Mini Binder Clip x 3
  • Small wooden sticks

2.2 Diagrams of experimental setup

The food colouring dyes on a petri dish

Extraction of Skittle Dyes

2.3 Procedures

    1. Choose three colors of candies you want to test.
    2. Use a pencil to light label which candy color or food coloring will be spotted on each paper strip.
    3. Label chromatography strips for each candy color.
    4. Draw a pencil line 1 cm from the edge of each strip of paper, which is the origin line.
    5. Fill the conical flask with some water.
    6. Put a single drop of water in the petri dish.
    7. Leave the candy in the drop of water to allow the dye to dissolve.
    8. Remove the candy, then dip a wooden ice-cream stick into the now-colored                           drop of water.
    9. Spot the candy dye solution onto the chromatography strip by touching the wooden ice-cream stick.    
    10. Allow the spot on the strip to dry.                      
    11. Let the solvent rise up the strip (by capillary action) and wait for 10 minutes for the dye and the solvent to rise up the filter paper.
    12. Keep a close eye on the chromatography strip and the solvent front— if you let it run too long the dye may run off the paper and become distorted.  
    13. Prepare chromatography strips with food coloring dyes.
    14. For each food coloring color put a drop of coloring with a drop of water in the bottom of the petri dish.
    15. Dip a wooden ice-cream stick into the drop of food coloring.
    16. Spot the food coloring onto a chromatography strip by touching the stick to the strip right in the center of the origin line.
    17. Repeat step 2 to 14 (three times for every skittle color)
    18. Repeat steps 13 to 16 with other food colouring dyes (three times for every food colouring)
    19. After 10 minutes, use a pencil to mark how far the solvent rose.
    20. Compare the Rf values for the candy colors and the food coloring dyes.

2.4 Risk Assessment and Management  

Skittles that are brought to the lab should not be consumed
Do not eat the skittles that are used in the experiment.
As the experiment involves glassware, there is a risk of breakage and cutting off the hands.
Wear gloves when carrying out the experiment. In case of breakage, the cut to the hands will be minimized.
When using scissors to cut the chromatography paper, might cut yourself.
Be careful and put the scissors away when done.
When using the wooden toothpicks, might poke yourself and cause injuries.
While using the wooden toothpick, use it carefully.

2.5 Data Analysis

1.    Tabulate the data using a table and from the results that are on the table, calculate the Rf of each dye. After that, calculate the average value.

2.    From the table, you will use the Rf value to compare the "unknown" components of colored candy dyes with the known components of food coloring dyes. Since there are only a small number of approved food dyes, you should be able to identify the ones used in the candies by comparison to the chromatography results for food coloring.

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