Murder Lab

Situation:

Yesterday at 3 AM, at Mike's Awesome Bakery in Francestown, NH the baker arrived to find his assistant baker dead: lying in a pool of blood.  The victim's body was covered in a white powder.  

In an attempt to find the source of the white powder, investigators collect multiple samples from the bakery (baking soda, flour, baking powder, powdered milk, cornstarch).

Investigators are in the process of interviewing employees of the bakery to narrow their field of suspects.  They are also gathering clothing samples from employees to find a match for the white powder.

Materials at your disposal:

- baking soda
- baking powder

- flour

- cornstarch

- vinegar

- iodine solution

- universal indicator

- water

- lab materials (beakers, stirrers, pipettes, etc.)

Objective:

To identify the unknown substance (powder) covering the body.

Procedure:

1. Gather and arrange materials (see materials list, and picture)

2. Test the reaction that baking soda has with water, vinegar, iodine (add 2 drops to each powder)

3. Repeat step 2 for each substance

4. Test the pH of each substance

- Add 2 drops of the universal indicator to each substance

- Record the reaction

- Compare to the other substances

5. Look at all the data

6. Conclude, and complete lab sheet

Analysis: Complete the data table below.

Table:

Test Solutions	Baking Soda	Baking Powder	Flour	Cornstarch	Unknown
Water	Stayed on top (No reaction)	Absorbed (Physical reaction)	Stayed on top (No reaction)	Stayed on top (No reaction)	Absorbed (Physical reaction)
Vinegar	Fizzed, created a bubble (Chemical reaction)	Fizzed a little (Chemical reaction)	Stayed on top (No reaction)	Stayed on top (No reaction)	Fizzed a little (Chemical reaction)
Iodine	Soaked in (Physical reaction)	Turned purple, fizzed (Physical and chemical reaction)	Turned dark purple (Chemical change)	Turned purple (Chemical change)	Turned purple (Chemical change)
Indicator	Turned green (Chemical change)	Turned yellow/ orange (Chemical change)	Turned red (Chemical change)	Turned red (Chemical change)	Turned yellow/ orange (Chemical change)

Conclusion:

The investigators should look for baking soda when examining the suspects clothing. The physical and chemical changes of baking powder and the unknown substance were the same. As well as that, both substances have the same physical appearance.