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Question
Give a reason why – Heating a platinum wire is a reversible change but, heating a magnesium wire is an irreversible change.
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Solution
Heating a platinum wire, the final product is again platinum wire (as platinum is a noble metal and does not react with air), i.e. no change in composition and is a physical change. Heating magnesium wire forms MgO i.e. composition changes a new substance white powder of magnesium oxide is formed is a chemical change.
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