What is Matter in Our Surroundings Class 9: Complete Guide

Definition of Matter in Our Surroundings

Matter is anything that has mass and occupies space. It is the substance that makes up all physical objects around us—from the air we breathe to the water we drink and the chair we sit on. In Class 9 NCERT Science, matter is introduced as the basic concept to understand physical science.

Key points about matter:

• Has mass (measured in kilograms or grams)
• Occupies volume (measured in litres or cubic metres)
• Exists in different states

Every object you see or touch is made of matter, including living beings and non-living things.

States of Matter: Solid, Liquid, and Gas

Matter exists mainly in three states: solid, liquid, and gas. Each state has distinct characteristics based on particle arrangement and movement.

Understanding these states helps explain everyday phenomena like ice melting or water evaporating.

Properties of Matter and Particle Theory

Matter has several properties that help us identify and classify it. These include:

• Mass: Amount of matter in an object
• Volume: Space occupied
• Density: Mass per unit volume, calculated as $\text{Density} = \frac{\text{Mass}}{\text{Volume}}$
• Compressibility: Gases are highly compressible; solids are not

Particle theory states that:

• Matter is made of tiny particles
• Particles have spaces between them
• Particles are always moving
• Particle movement increases with temperature

This theory explains why solids keep shape, liquids flow, and gases expand.

Changes in States of Matter

Matter can change from one state to another when energy (usually heat) is added or removed. These changes are physical and reversible.

Common changes include:

• Melting: Solid to liquid (e.g., ice to water)
• Freezing: Liquid to solid (water to ice)
• Evaporation: Liquid to gas (water to steam)
• Condensation: Gas to liquid (steam to water)
• Sublimation: Solid to gas without liquid phase (dry ice)

Example: When ice at 0 °C melts, it absorbs heat but its temperature remains constant until fully melted.

Difference Between Physical and Chemical Changes

Matter undergoes two main types of changes:

In Class 9 Science, understanding this difference is crucial for identifying matter transformations in daily life.

Examples of Matter in Our Surroundings

Matter is present everywhere in our surroundings. Some common examples include:

• Air (gas mixture)
• Water (liquid)
• Ice (solid)
• Soil (solid mixture)
• Metals like iron and copper (solids)

Everyday materials you use, such as clothes, food, and furniture, are forms of matter. Recognising these helps relate theoretical concepts to real life.