Question

is taken in place of potassium chloride
9. Give a reason why -
a) Heating a platinum wire is a reversible change but, heating a magnesium wire is an
ireversible change.
b] Addition of zinc nitrate to water is a physical change but, addition of zinc to dilute nitric
acid is a chemical change.
c) Rusting of iron is a chemical change but, magnetization of iron is a physical change.


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Answer 1

Answer:

(a) When Platinum gets heated, it changes color. When cooled it retains its earlier color and it does not react easily with oxygen in the air. Magnesium reacts with Oxygen in the air and forms magnesium oxide which cannot be undone.

(b) Zinc nitrate (soluble in water) dissolves in water and is reversible. No change in composition takes place is a physical change whereas zinc reacts with dil. nitric acid to produce H2 gas which gets oxidized to water by nitric acid (oxidizing agent) and hence is a chemical change.

(c) magnetization of iron is a physical change while rusting of iron is a chemical change. ... hence a chemical change. Whereas, iron bar gets magnetised only when it is in vicinity of a magnet and is a reversible process, hence it is a physical change .

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Explanation:

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