7. Fill wells B, E, and H with vinegar. Record any changes yo observe.

8. Add one drop of iodine solution to wells C, F, and I. Record any changes yo observe. CAUTION Iodine solution is corrosive and poisonous. It can stain skin and clothing. Rinse any iodine spills with water.

Part B: Properties of Unknown Substances

1. Predicting Look at the sample from the crime scene and the sample from the suspect's shoe. Based on your observations, predict whether testing will show that the samples are identical. Record your prediction.

2. Use a clean spatula to place a small amount of the sample from the crime scene in wells J, K, and L. Record any physical properties of the sample that yo observe.

3. Use a clean laboratory spatula to place a small amount of the sample from the suspect's shoe in wells M, N, and O. Record any physical properties of the sample that you observe.

4. Fill wells J and M with water. Record your observations.

5. Fill wells K and N with vinegar. Record your observations.

6. Add one drop of iodine solution to wells L and O. Record your observations.

7. Rinse all materials off the spot plates and flush them down the drain with at least ten times as much water. Dispose of your plastic gloves as directed by your teacher. CAUTION Wash your hands thoroughly with soap or detergent before leaving the laboratory.

Analyze and Conclude

1. Analyzing Data Were yo able to use the ability to dissolve in water to distinguish all three materials? Explain.

2. Drawing Conclusions Are the samples from the suspect and from the crime scene identical?

3. Evaluating and Revising Did the data yo collected support your prediction? Explain your answer.

Go Further Design an experiment to determine the effect of heating on the materials you tested in this lab. With your teacher's approval and supervision, carry out your experiment and use the data you collect to identify a sample of an unknown material.

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