Matter in Our Surroundings Class 9 Science — Revision Notes
This chapter introduces matter and its states: solid, liquid, and gas. Students learn about physical properties, state changes, and the particle model of m
TL;DR: This chapter introduces matter and its states: solid, liquid, and gas. Students learn about physical properties, state changes, and the particle model…
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This chapter introduces matter and its states: solid, liquid, and gas. Students learn about physical properties, state changes, and the particle model of m
States of Matter
- Solid: definite shape, definite volume, particles tightly packed, no flow
- Liquid: no definite shape, definite volume, particles loosely packed, can flow
- Gas: no definite shape, no definite volume, particles far apart, high mobility
- Plasma: fourth state with ionized particles (beyond Class 9 scope)
Properties of Matter
- Mass: amount of matter in substance
- Volume: space occupied by matter
- Density: mass per unit volume (d = m/v)
- Density of water = 1 g/cm^3 or 1000 kg/m^3
Change of State
- Melting: solid to liquid (requires heat)
- Freezing: liquid to solid (releases heat)
- Evaporation: liquid to gas (requires heat)
- Condensation: gas to liquid (releases heat)
- Sublimation: solid directly to gas (e.g., dry ice)
Particle Model
- All matter made of tiny particles
- Particles have spaces between them
- Particles are in continuous motion
- Particles attract each other
- Temperature increases particle motion
Key Terms
- Matter: Anything that has mass and occupies space
- Density: Mass per unit volume of substance
- Evaporation: Process of liquid changing to gas at any temperature
Frequently Asked Questions
Why does matter have different states?
Difference in particle motion and spacing. Solids have tightly packed particles with low motion. Liquids have loosely packed particles. Gases have far-apart particles with high motion.
What is difference between evaporation and boiling?
Evaporation occurs at any temperature at surface of liquid. Boiling occurs throughout liquid at fixed temperature (boiling point) with bubbles forming.
More Class 9 Science Revision Notes
- Is Matter Around Us Pure
- Atoms and Molecules
- Structure of the Atom
- The Fundamental Unit of Life
- Tissues
- Motion
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