Question

Classify the following as chemical or physical changes: • cutting of trees, • melting of butter in a pan, • rusting of almirah, • boiling of water to form steam, • passing of electric current, through water and the water breaking down into hydrogen and oxygen gases, • dissolving common salt in water, • making a fruit salad with raw fruits, and • burning of paper and wood. NCERT Class 9th Science Ch 2 Is Matter Around Us Pure

Answer 1

Cutting of trees and making fruit salad are physical changes, while melting butter, boiling water, passing electric current through water, dissolving salt, rusting of almirah, and burning paper and wood are chemical changes.

Step-by-step explanation:

The following are classifications of the given changes as either chemical or physical:

1. Cutting of trees: This is a physical change as the structure of the trees changes, but no new substance is formed.
2. Melting of butter in a pan: This is a physical change as the butter changes from a solid to a liquid state without any change in its composition.
3. Rusting of almirah: This is a chemical change as the metal reacts with oxygen to form a new substance, iron oxide (rust).
4. Boiling of water to form steam: This is a physical change as water changes from a liquid to a gaseous state without any change in its composition.
5. Passing electric current through water: This is a chemical change as the water molecules break down into hydrogen and oxygen gases through the process of electrolysis.
6. Dissolving common salt in water: This is a physical change as the salt particles disperse evenly throughout the water without any change in their composition.
7. Making a fruit salad with raw fruits: This is a physical change as the fruits are physically mixed together without any change in their composition.
8. Burning of paper and wood: This is a chemical change as the paper and wood undergo combustion and combine with oxygen to form new substances, such as carbon dioxide and water vapor.

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