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Matter in our surroundings
Chemistry class 9 NCERT CBSE
1. What is Matter?
Anything that occupies space and has mass is called matter.
Examples: Solids, liquids, gases.
Mass – quantity of matter in an object.
Volume – space occupied by an object.
2. States of Matter
Three main states:
, 1.Solid
Fixed shape & volume
Particles are closely packed and vibrate in place
Example: Ice, wood
2.Liquid
Fixed volume, takes shape of container
Particles are less tightly packed than solids; can move/slide
Example: Water, milk
3.Gas
No fixed shape or volume, fills container completely
Particles are far apart and move freely
Example: Oxygen, nitrogen
Important: Some NCERT questions ask differences between states → always remember in table
form.
3. Properties of Matter
Elasticity: Ability to regain original shape after force.
Density (ρ): Mass/Volume
Compressibility: Solids & liquids – low, gases – high
Diffusion: Gases mix quickly; liquids – slower; solids – very slow
Quick Tip: Remember solids < liquids < gases for diffusion rate.
4. Change of State
Melting: Solid → Liquid
Freezing: Liquid → Solid
Vaporisation: Liquid → Gas
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Matter in our surroundings
Chemistry class 9 NCERT CBSE
1. What is Matter?
Anything that occupies space and has mass is called matter.
Examples: Solids, liquids, gases.
Mass – quantity of matter in an object.
Volume – space occupied by an object.
2. States of Matter
Three main states:
, 1.Solid
Fixed shape & volume
Particles are closely packed and vibrate in place
Example: Ice, wood
2.Liquid
Fixed volume, takes shape of container
Particles are less tightly packed than solids; can move/slide
Example: Water, milk
3.Gas
No fixed shape or volume, fills container completely
Particles are far apart and move freely
Example: Oxygen, nitrogen
Important: Some NCERT questions ask differences between states → always remember in table
form.
3. Properties of Matter
Elasticity: Ability to regain original shape after force.
Density (ρ): Mass/Volume
Compressibility: Solids & liquids – low, gases – high
Diffusion: Gases mix quickly; liquids – slower; solids – very slow
Quick Tip: Remember solids < liquids < gases for diffusion rate.
4. Change of State
Melting: Solid → Liquid
Freezing: Liquid → Solid
Vaporisation: Liquid → Gas
2
