Analyzing+food-coloring+additives

__**//Analyzing food-coloring additives//**__ **Lab Procedure** (35 minutes):
 * Purpose: ** The purpose of this lesson is to identify the unnatural food-coloring additives in various commercial candies, and to understand why these artificial coloring agents are bad for your body.
 * Objectives: **
 * 1) Students will recognize that many candies contain artificial coloring agents to enhance their visual appeal.
 * 2) Students will perform an investigation to analyze the food dyes in two commercial candies and compare them with dyes in food coloring products.
 * 3) Students will separate and identify food dyes by paper chromatography.
 * Action Plan: **
 * Students will complete the following lab activity to analyze food-coloring additives.
 * Materials: **
 * Food coloring packet
 * Two different commercial candies
 * Well plates
 * Toothpicks
 * Chromatography paper
 * Small glass jar with lid
 * 1) <span style="background-color: white; font-family: Arial,sans-serif; font-size: 10pt;">Obtain one piece of two different commercial candies and a food-coloring sample (same color).
 * 2) <span style="background-color: white; font-family: Arial,sans-serif; font-size: 10pt;">Put each candy into a well of a well-plate and label each one.
 * 3) <span style="background-color: white; font-family: Arial,sans-serif; font-size: 10pt;">Add 5-10 drops of water to each well and then stir the mixture with a toothpick. //Make sure the colored coating is completely dissolves from the candy.//
 * 4) <span style="background-color: white; font-family: Arial,sans-serif; font-size: 10pt;">Add 3-4 drops of food coloring sample to a third well and label it.
 * 5) <span style="background-color: white; font-family: Arial,sans-serif; font-size: 10pt;">Obtain a strip of chromatography paper. //With a pencil, draw a horizontal line 2 cm from the bottom of the paper strip and another horizontal line 3 cm from the top.//
 * 6) <span style="background-color: white; font-family: Arial,sans-serif; font-size: 10pt;">Place a spot of each dye solution on the bottom line with toothpicks. Reapply the spot. //You will have three spots along the bottom line of the chromatography paper.//
 * 7) <span style="background-color: white; font-family: Arial,sans-serif; font-size: 10pt;">Obtain a chromatography chamber and fill it with the solvent (water) to a depth of 1 cm.
 * 8) <span style="background-color: white; font-family: Arial,sans-serif; font-size: 10pt;">Lower the chromatography paper’s bottom edge into the solvent. //Be sure the colored spots remain above the solvent surface.// Cover the chamber.
 * 9) <span style="background-color: white; font-family: Arial,sans-serif; font-size: 10pt;">Once the solvent has moved up the paper, remove the paper from the chamber, and mark the solvent’s path using a pencil.
 * 10) <span style="background-color: white; font-family: Arial,sans-serif; font-size: 10pt;">Record the colors observed for the dye sample and candy solutions.
 * 11) <span style="background-color: white; font-family: Arial,sans-serif; font-size: 10pt;">Measure the distance (in cm) from the initial pencil line where you placed the spots to the center of each dye spot. //Record these distances in your lab report//.
 * 12) <span style="background-color: white; font-family: Arial,sans-serif; font-size: 10pt;">Measure and record the distance (in cm) that the solvent moved.
 * 13) <span style="background-color: white; font-family: Arial,sans-serif; font-size: 10pt;">Calculate the Rf value of each dye spot you observed. //Record these values in lab report.//
 * <span style="background-color: white; font-family: Arial,sans-serif; font-size: 10pt;">Students will answer the following questions as an exit ticket before they leave the class (5 min).
 * <span style="background-color: white; font-family: Arial,sans-serif; font-size: 10pt;">Based on your data, do any of the three samples contain any of the same dyes?
 * <span style="background-color: white; font-family: Arial,sans-serif; font-size: 10pt;">What evidence did you use to verify this?
 * <span style="background-color: white; font-family: Arial,sans-serif; font-size: 10pt;">The candy and food-coloring packages list each dye that they contain. Compare this information with your experimental results.
 * <span style="background-color: white; font-family: Arial,sans-serif; font-size: 10pt;">What similarities did you find?
 * <span style="background-color: white; font-family: Arial,sans-serif; font-size: 10pt;">What differences did you find? What are possible reasons for them?

<span style="background-color: white; font-family: Arial,sans-serif; font-size: 10pt;">**Homework:** Students will listen to the [|“What the world eats” podcast] and go to World hunger unit wikispace to reflect on it in a class blog in preparation for the next class.