state a revelant reason for the following:
1. An iron nail kept open in the atmosphere rusts is a chemical change.
2. A piece of magnesium strip is dropped into a beaker containing dilute
hydrochloric acid, is a chemical change.
3. Rusting of iron is a chemical change but, magnetization of iron is a pysical change.
4. Heating a platinum wire is a reversible change, but, heating a magnesium wire is
an irreversible change.
5. Addition of zinc nitrate to water is a physical change but, addition of zinc to dilute
nitric acid is a chemical change.
Answers
Answer:
1. Rusting of iron is a chemical change because it happens due to a chemical reaction between iron and air in presence of moisture. If the chemical reaction hadn't taken place between them, the iron wouldn't have rusted and acquired brown texture from its dull grey one.
2. A Piece of Magnesium Strip is dropped into a beaker containing dilute Hydrochloric acid because it is an example of reaction between an acid and a metal. This produces a corresponding metal salt and HYDROGEN gas is evolved.
3. Rusting of iron is a chemical change because rust is formed during the chemical reaction but in magnetization of iron no new substance is formed during the reaction.
4. A platinum wire is a reversible change because it can be reversed but heating a magnesium wire is an irreversible change because it cannot be reversed.
5. When Zinc nitrate is pored in the water it does not react with water. It dissociates into the ions Zn⁺ and NO₃²⁻ . No zinc hydroxide is formed. Thus addition of Zinc nitrate into the water is a Physical change, as chemical properties of zinc nitrate in water remain as such.
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