Crocker

1/28/10

The Mystery of the Missing Mascot

Megan Crocker

Grades 3-7

Teaching Objectives:

  1. To teach students to think through problems and use various methods to solve for unknown variables.
  2. To teach students how various chemical reactions and physical changes can be tools in solving problems.

Definitions:

  1. Physical change- when an object undergoes a change that does not affect its chemical structure; for example, when water goes from a solid to a liquid.
  2. Chemical change- when an object undergoes a chemical reaction and emerges with a different structure than when it began.

Materials:

  1. Screw-top jars
  2. Iodine crystals
  3. Tape
  4. Magnifying glass
  5. Cornstarch
  6. Water
  7. Baking soda
  8. Flour
  9. Sugar
  10. Salt
  11. Baking powder
  12. Iodine
  13. Vinegar
  14. Snow
  15. pH meter

Procedure:

Tell the students that a crime has been committed at their school, but the Maine Police Department has recruited them to run forensic tests on the evidence they uncovered. They recovered a fingerprint from the scene, a mysterious white powder, and water from some puddles on the floor. Their job is to study the evidence and, using the provided suspect profiles, make objective conclusions.

  1. Fingerprint station
  2. Take one of the provided suspect prints out of the bag. Be careful to handle it by the edges so that you can avoid contamination.
  3. Without covering the thumbprint, tape the paper to the side of the jar and screw on the lid.
  4. Wait 3-5 minutes, or until you can see the thumb print clearly.
  5. While you are waiting, mix together 1 teaspoon of cornstarch with 3 teaspoons of water (this mixture should be really soupy).
  6. When you take the thumbprint out of the jar, it should be visible and a brown color. Using a cotton swab, brush a thin layer of the cornstarch-water solution over it and wait for it to dry. This fixes the thumbprint because the iodine vapors would eventually diffuse off the paper into the air.
  7. When you have a good thumbprint, compare it to the suspect profiles using a magnifying glass and see if you can find whose thumb left a print.
  8. Resolving the White Powder
  9. Put a small amount of each of the powders—sugar, flour, baking soda, baking powder, salt, and cornstarch—into a well on the spot plate as shown by the following diagram.
  1. Take observations of each of the powders and of the mysterious white powder. Compare these observations. Which two can you automatically eliminate without further testing?
  2. Add 5 drops of iodine to each of the remaining samples in the spot plate (this should be flour, baking soda, baking powder, and cornstarch) and take observations. Iodine binds to starch molecules and turns them purple, so all the compounds containing starch turned purple.
  3. When the iodine was added to the baking powder, there should have been bubbles forming. This is because the baking powder is reacting with the water in the iodine solution.
  4. Baking soda is the only one that does not turn purple, but you can add a few drops of vinegar to the well just to make sure. The bubbles let you know that it is reacting.
  5. The last two, flour and cornstarch, both turned purple and look almost the same. The cornstarch however, became a darker purple than the flour and this is how you can tell them apart.
  6. Now follow this same process using a little bit of the unknown white powder.
  1. Mysterious Puddles
  2. Take a sample of the mystery puddle and place it into a small, plastic cup.
  3. Take two handfuls of snow and put them in two plastic cups.
  4. Place a thermometer in each cup filled with snow.
  5. Pour and mix 3 teaspoons of salt into one of the cups and see which snow melts faster and has a higher temperature.
  6. Now test the pH of the mystery puddle using the pH meter.

Resources:

ted/labs/Finger%2520Print%2520Lab.doc+fingerprint+lab&cd=5&hl=en&ct=clnk&gl=u

  • Except for Kevin’s, I took the various fingerprints from online. To get my fingerprint in as Kevin’s, I pressed my thumb into an inkpad, then placed it on a piece of paper and scanned it into the computer.

SUSPECT #1

NAME: Jean the Lunch Lady

AGE: 44 years old

BIRTHDAY: 6-17-1965

HEIGHT:5’11”

WEIGHT:135 lbs

HAIR COLOR: Blonde

EYE COLOR: Blue

INFORMATION:

  • Jean bakes so she is regularly exposed to flour, baking soda, baking powder, salt, sugar, and cornstarch.
  • Jean does not use salt in her driveway, so she would not have tracked salt into the room.
  • At the time of the theft, Jean was seen taking the trash outside to the dumpster, which is right outside the gymnasium!

FINGERPRINT:

SUSPECT #2

NAME: Kevin the Custodian

AGE: 56 years old

BIRTHDAY: 10-21-53

HEIGHT: 6’2”

WEIGHT: 195 lbs.

HAIR COLOR: Grey

EYE COLOR: Brown

INFORMATION:

  • Kevin uses baking soda to clean up spills in the chemistry department.
  • Kevin puts salt down on the school walkways.
  • He was seen coming out of the gymnasium carrying a large duffel bag seconds before the mascot was discovered missing!
  • He claims, however, that he could not have taken it because he would have tracked in snow, but it was already melted when he came out of the gym. Snow does not melt that fast!

FINGERPRINT:

SUSPECT #3

NAME: Ms. Fredette the Substitute Science Teacher

AGE: 57 years old

BIRTHDAY: 1-7-1953

HEIGHT: 5’7”

WEIGHT: 125 lbs.

HAIR COLOR: Grey

EYE COLOR: Green

INFORMATION:

  • Ms. Fredette used baking powder in her class today to show how baking powder and water react.
  • Ms. Fredette has been teaching classes all day except for when she took a lunch break, but no one remembers seeing her in the cafeteria.

FINGERPRINT:

SUSPECT #4

NAME: Mr. Frederickson the Vice Principal

AGE: 42 years old

BIRTHDAY: 8-24-1967

HEIGHT: 6’3”

WEIGHT: 185 lbs.

HAIR COLOR: Brown

EYE COLOR: Brown

INFORMATION:

  • Mr. Frederickson always puts a large amount of sugar in his coffee so he may have left some at the scene of the crime.
  • At the time of the crime, he was seen carrying a cup of coffee and heading toward the teacher’s lounge, which is right next to the gymnasium.

FINGERPRINT:

The Case of the Missing Mascot

You and your classmates have been recruited by the Maine Police Department to help them solve a case. Your precious school mascot has been stolen from the gymnasium by one of four suspects and it needs to be recovered for the game tonight! A mysterious white powder was recovered from the scene as was a fingerprint and a liquid from a puddle on the floor. Follow the evidence and make your accusation from the suspect profiles! Each profile contains their fingerprint, where they were at the time of the crime, and what white powder each person was exposed to.

Procedure:

Mysterious White Powder

  1. Set up your spot plate as shown in the diagram below by placing a small amount of each powder in the well.
  1. Take observations of the six powders and the mystery powder and write them on your Observations sheet. Which two of the six powders can you automatically eliminate?
  2. Take a dropper and add 5 drops of iodine to each of the remaining wells. The cornstarch, baking powder, and flour should turn purple and the baking soda should do nothing at all.
  3. When you added the iodine, the baking powder should have begun fizzing and the cornstarch should be a darker purple than the flour.
  4. To make sure it is baking soda, add a couple drops of vinegar to the baking soda and you should see bubbles.
  5. Follow this same procedure with the mystery powder. Use these observations to determine what the powder actually is!

Fingerprint

  1. Take one of the provided suspect prints out of the bag. Be careful to handle it by the edges so that you can avoid contamination.
  1. Without covering the thumbprint, tape the paper to the side of the jar and screw on the lid.
  2. Wait 3-5 minutes, or until you can see the thumb print clearly.
  3. While you are waiting, mix together 1 teaspoon of cornstarch with 3teaspoons of water.
  4. When you take the thumbprint out of the jar, it shouldbe visible and a brown color. Using a cotton swab, brush a thin layer of the cornstarch-water solution over it and wait for it to dry.
  5. When you have a good thumbprint, compare it to thesuspect profiles using a magnifying glass and see if you can find whose thumb left a print.

Mystery Puddle

  1. Take two handfuls of snow and put them in two plastic cups.
  2. Place a thermometer in each cup.
  3. Pour 3 teaspoons of salt into one of the cups and see which snow melts faster and has a higher temperature. Record this on your Data Sheet.
  4. Test the pH of the mystery puddle with the pH meter.

Now you are ready to make your accusation. Using the evidence that you uncovered, combine it and make a case proving who did it!

Observations

Sugar
Flour
Baking Soda
Baking Powder
Salt
Cornstarch
Mystery Powder

Student Data Sheet

  1. Which snow melted faster, the one with salt in it or the one without?

______.

  1. What was the pH of the mystery puddle?

______.

  1. Write out a flowchart for how you discovered what each of the powders were.
  1. What was the mystery powder?

______.

  1. Whose fingerprint was it?

______.

  1. How do you know? ______.
  1. Who stole the school mascot?

______.

  1. What evidence do you have?

______.

Mystery Solution

In this theft, the culprit was…. Kevin the Custodian! He left behind some baking soda that he used to clean up an acid spill in the chemistry lab and he left behind a perfect fingerprint! He claimed, however, that he could not have done it because the snow would not have melted between when he entered the gym and when he was seen leaving it. We know now, through our experiment, that salt in the snow makes it melt faster. This means that it was possible that Kevin was in the gym at the time of the theft. All this evidence pointed to Kevin’s guilt and when you told the Maine Police Department your proof, they found the mascot hidden in Kevin’s car!

Congratulations! You solved the case!

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