Third Experiment: Forensics Lab

Lab Design Sheet

Name of Experiment: Murder! (Who did it? A forensics lab)

Prior Knowledge: On March 6th at 3 am, an assistant baker at Mike’s Awesome Bakery in Francestown, NH was found dead lying in a pool of blood. The assistant baker was found covered in a mysterious white powder, which our Earth Science class must identify.

Investigators collected samples of white powder they found in the bakery (baking soda, baking powder, flour, cornstarch, and the unknown substance found on the body).

As well as collecting substance samples, the investigators interviewed employees of the bakery and took clothing samples to see if any employee had traces of the substance on their person.

Objective: Identify the unknown substance

Equipment:

• baking soda
• baking powder
• flour
• cornstarch
• unknown
• vinegar
• iodine solution
• universal indicator
• water
• lab materials (beakers, stirrers, pipettes, etc)

Procedure:

1. Arrange materials
1. Collect samples of baking powder, baking soda, flour, cornstarch, and the unknown substance along with a plastic-covered data sheet
2. Collect five Popsicle sticks and four pipettes, one each for water, vinegar, iodine, and universal indicator
3. Line up corresponding substances with Popsicle sticks placed above their columns on the data sheet
4. Use corresponding Popsicle sticks to spoon small piles of each substance onto the data table
2. Test baking soda
1. Test reaction with water
1. Squeeze 3 to 5 drops of water onto the baking soda with a pipette
2. Study and record the reaction
3. Repeat steps 2a to 2b with vinegar, iodine, and universal indicator
3. Test baking powder
1. Repeat step 2 accordingly
4. Test flour
1. Repeat step 2 accordingly
5. Test flour
1. Repeat step 2 accordingly
6. Test cornstarch
1. Repeat step 2 accordingly
7. Test unknown
1. Repeat step 2 accordingly
8. Clean up materials
9. Analyze collected data
10. Finalize conclusion and complete lab sheet

DATA:

	Baking Powder	Baking Soda	Flour	Cornstarch	Unknown
Water	NO REACTION	CHEMICAL REACTION: Mixture fizzes/ bubbles	PHYSICAL REACTION: Water runs off, mixture becomes glue-like	PHYSICAL REACTION: Changes texture, becomes tacky	CHEMICAL REACTION: Mixture fizzes/ bubbles
Vinegar	CHEMICAL REACTION: Mixture fizzes/ bubbles, vinegar consumes baking soda	CHEMICAL REACTION: Mixture fizzes, but baking powder is more resistant to vinegar than baking soda	NO REACTION	NO REACTION	CHEMICAL REACTION Mixture fizzes and grows
Iodine Solution	NO REACTION: Iodine does not change color	CHEMICAL REACTION: Some bubbles; mixture becomes a dark purple/ indigo, lightens	CHEMICAL REACTION: Mixture becomes a gray/navy/ purple color	CHEMICAL REACTION: Mixture becomes a dark indigo, then lightens	CHEMICAL REACTION: Some bubbles; mixture becomes a dark purple/ indigo, lightens
Universal Indicator	CHEMICAL REACTION: Teal/green color becomes blue; no movement; pH 9	CHEMICAL REACTION: Red to orange to yellow to green; pH 7?	CHEMICAL REACTION: Orange color; pH 4	CHEMICAL REACTION: Pinkish-red color; ph 3	CHEMICAL REACTION: Orange to yellow to green; pH 7?km

CONCLUSION: The investigators should be looking for baking soda on the suspects' clothing. We determined this by comparing the presence, type, and details of each substance's reaction with water, vinegar, iodine, and universal indicator. Both baking powder and the unknown had a chemical reaction with every reactant that we tested; this was not the case for any other prospective substance. Additionally, the pH was the same between baking powder and the unknown, and the details were the same for every other reaction.