Question

notes of chapter is matter around us pure class 9 ​

Answer 1

Notes:

Pure substances

• Pure substances are elements or compounds.

• They are made up of only one kind of entity.

• They cannot be broken down into simpler entities by chemical or physical methods.

• They have a fixed composition.

Example: Diamond, carbon dioxide

Mixtures

• Mixtures are formed by just mixing two or more pure substances (components) such that each substance retains its own chemical identity.

Types:

1. Homogeneous mixture

A mixture that has a uniform composition throughout is called a homogeneous mixture or solution.

Examples: sugar in water, salt in water.

Heterogeneous mixture

A mixture that contains physically distinct parts and has a non-uniform composition is called a heterogeneous mixture.

Examples: Mixture of salt and iron filings, sand and sugar.

Physical and chemical changes

A substance is said to undergo a physical change when only the physical properties such as the shape, size, color, or state of the substance change. No new substance is formed.

Example: Melting of ice, boiling water.

A substance is said to undergo a chemical change when a new substance with completely new properties (physical and chemical) is formed.

Example: Burning of wood or paper, souring of milk.

Answer 2

Answer:

it is there,

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