# World of Chemistry

## Educators

Problem 1

Review how we defined chemical change in Chapter $3 .$ Explain how the visual clues mentioned in this chapter are indicators of chemical change as defined in Chapter 3 .

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Problem 2

If a piece of blackboard chalk is heated strongly, the mass of the chalk decreases substantially, and the chalk is converted into a fine powder. What evidence is there for a chemical reaction having taken place when the chalk is heated?

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Problem 3

If you have had a clogged sink drain at your home, your parents may have have tried using a commercial drain cleaner to dissolve the clog. What evidence is there that such drain cleaners work by chemical reaction?

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Problem 4

If a bottle of aspirin is left open to the air, eventually one of the products is acetic acid (vinegar is a mixture of acetic acid and water). Is there evidence that this change represents a chemical reaction?

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