1. Using Chemical Change to Identify an Unknown
6/15/2018 9:34 AM
Using Chemical Change to Identify an Unknown
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2. Binder page 12A
Objectives:
To be able to identify and control variables to develop a test to identify an unknown powder.
To be able to explain that a substance reacts chemically in characteristic ways and that these characteristics can be used to identify an unknown substance.

3. Demonstration:
Both powders looked similar at first. How do you know that they are different?
Which do you think is probably a chemical change?
What other tests could you conduct with baking soda and cornstarch to compare their characteristic properties?
Answer questions 1 and 2 on Lab Activity Sheet

4. ACTIVITY:
In this activity you will test four different similar-looking powders with four different test solutions.
The four powders are baking soda, baking powder, cream of tartar, and cornstarch.
The four test solutions are water, vinegar, iodine solution, and universal indicator.
Each powder will react in a certain way with each solution used to test it. Each powder and solution pair is one set of reactants.
In some cases, no chemical reaction will occur.

5. Unknown Powder
The unknown is one of the four powders you have tested and your job is to find out which one.
How could you test the unknown powder so that you could identify it?

6. EXTEND:
Identify the two substances in baking powder that make it bubble when water is added.

7. Key Concepts: Substances react chemically in characteristic ways.
A set of reactions can be used to identify
an unknown substance.