Question

Which laboratory activities involve chemical changes?

Answer 1

leaving a copper penny in vinegar until it turns green

Step-by-step explanation:

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Answer 2

The green growing on the penny of copper and the rust forming on the nail of iron are chemical changes.

Boiling away salt water, scraping iron filings from a mixture of sand with a magnet, and breaking a rock with a hammer, are physical changes.

Extracting iron filings from a mixture of sand with a magnet is absolutely no change. That's merely separating items that got mixed up.