Question

Which laboratory activity involves a chemical change? leaving a copper penny in vinegar until it turns green boiling saltwater for several minutes until only solid salt remains extracting iron filings from a sand mixture using a magnet crushing a rock with a hammer to extract mineral deposits

Answer 1

Answer:

leaving copper penny in vinegar

Explanation:

the others are physical changes. when copper penny is put in vinegar, a reactive oixde layer is formed which is green in colour. namely, Cu(II) acetate.

Answer 2

Final answer: The laboratory activity: leaving a copper penny in vinegar until it turns green, involves a chemical change.

Given that: We are given laboratory activities: leaving a copper penny in vinegar until it turns green, boiling saltwater for several minutes until only solid salt remains, extracting iron filings from a sand mixture using a magnet, crushing a rock with a hammer to extract mineral deposits.

To find: We have to find which laboratory activity involves a chemical change.

Explanation:

• The laboratory activity: leaving a copper penny in vinegar until it turns green, involves a chemical change. Copper form copper oxide when it exposed to air or oxygen, which make copper penny look dirty. So leaving a copper penny in vinegar help to break up this copper oxide and expose the pure copper on the penny. Thus leaving a copper penny in vinegar, a chemical reaction occurs and the penny turns green. Hence it is correct answer.

• The laboratory activity: boiling saltwater for several minutes until only solid salt remains, which involve a physical change. During the process of boiling saltwater for several minutes, it converts from one state to another and does not change its chemical composition. Hence it is wrong answer.

• The laboratory activity: extracting iron filings from a sand mixture using a magnet, which involve a physical change. This is because the chemical composition of both sand mixture and iron filings does not change during the separation. Hence it is wrong answer.

• The laboratory activity: crushing a rock with a hammer to extract mineral deposits, which involve a physical change. This is because,  when rock salt is crushed, its chemical composition does not change but its physical properties changes. So it is a physical change. Hence this is wrong answer.

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