Name: ______Date: ______

CSI Case #122579: Cookie Ingredients Mystery

Attention, I need your help! I was planning on making a big batch of cookies and I weighed out the dry ingredients. Unfortunately I did not label the mixture and when I brought the bag to school it got mixed up with someone else’s chemistry experiment.

The cookie recipe is as follows:

Mix 15 cups of flour, 6 teaspoons of baking soda, 5 cups of powdered sugar, 3 pounds of butter, and 10 eggs in a large bowl. Then bake until golden brown.

In order to discover which bag contains the necessary cookie ingredients follow the procedure below.

Powder Testing Procedure

Important: Test one powder at a time and do not allow samples to mix.

For each sample:

  1. Place 3 small samples of each powder (about half the size of a dime) on a piece of wax paper or in separate wells in a spot plate.

1st spot 2nd spot3rd spot

  1. Describe your powder sample and write your observations in the chart.
  2. Add 4 to 5 drops of water to the 1st pile and mix using a clean toothpick. Record your observations in the chart.
  3. Add 4 to 5 drops of vinegar to the 2nd pile and mix using a clean toothpick. Record your observations in the chart.
  4. Add 4 to 5 drops of iodine to the 3rd pile and mix using a clean toothpick. Record your observations in the chart.

CAUTION: iodine will stain clothing, hands and anything it touches!!!

  1. For the heat test, place a small amount of powder on a clean square of aluminum foil. Bend the edges up to create a “cup” and hold onto it using a pair of tongs or tweezers. Hold the sample over a lit Bunsen burner for a few seconds. Record your observations in the chart.

CAUTION: use care when working with heat! Long hair must be tied back. Sleeves must be rolled up. Keep papers (and anything flammable) away from the flame. Goggles must be worn, since the powder may melt and splatter!

CLEAN UP YOUR AREA BEFORE YOU LEAVE!

Investigations:

In order to identify an unknown mixture we will make observations about known substances.

Part 1: Follow the directions to test each sample (# 1-6) with water, vinegar, iodine, and heat. Record your observations on the chart and complete the flow chart.

Sample / Description / Water test / Vinegar test / Iodine test / Heat test
Baking soda
Baking powder
Corn starch
Powdered sugar
Flour
Baby powder

Name: ______Date: ______

COOKIE MYSTERY REACTIONS FLOW CHART

Name: ______Date: ______

Part 2: Follow the same procedure to test the three Mystery Mixtures (A, B and C). Record your observations in the chart below. Use your results from Part 1 to determine which mixture is the sugar cookie mixture.

Sample / Description / Water test / Vinegar test / Iodine test / Heat test
A
B
C

Which mystery mixture is my cookie mix? ______

What did you observe to make this decision? (Be specific)

SOLUTIONSCSI Case #122579: Cookie Ingredients Mystery

Attention, I need your help! I was planning on making a big batch of cookies and I weighed out the dry ingredients. Unfortunately I did not label the mixture and when I brought the bag to school it got mixed up with someone else’s chemistry experiment.

The cookie recipe is as follows:

Mix 15 cups of flour, 6 teaspoons of baking soda, 5 cups of powdered sugar, 3 pounds of butter, and 10 eggs in a large bowl. Then bake until golden brown.

In order to discover which bag contains the necessary cookie ingredients follow the procedure below.

Powder Testing Procedure

Important: Test one powder at a time and do not allow samples to mix.

For each sample:

  1. Place 3 small samples of each powder (about half the size of a dime) on a piece of wax paper or in separate wells in a spot plate.

1st spot 2nd spot3rd spot

  1. Describe your powder sample and write your observations in the chart.
  2. Add 4 to 5 drops of water to the 1st pile and mix using a clean toothpick. Record your observations in the chart.
  3. Add 4 to 5 drops of vinegar to the 2nd pile and mix using a clean toothpick. Record your observations in the chart.
  4. Add 4 to 5 drops of iodine to the 3rd pile and mix using a clean toothpick. Record your observations in the chart.

CAUTION: iodine will stain clothing, hands and anything it touches!!!

  1. For the heat test, place a small amount of powder on a clean square of aluminum foil. Bend the edges up to create a “cup” and hold onto it using a pair of tongs or tweezers. Hold the sample over a lit Bunsen burner for a few seconds. Record your observations in the chart.

CAUTION: use care when working with heat! Long hair must be tied back. Sleeves must be rolled up. Keep papers (and anything flammable) away from the flame. Goggles must be worn, since the powder may melt and splatter!

CLEAN UP YOUR AREA BEFORE YOU LEAVE!

Name: ______Date: ______

SOLUTIONSCOOKIE MYSTERY REACTIONS FLOW CHART

Name: ______Date: ______