Matter in Our Surroundings Class 9 Notes Science - Chapter 1

Chapter: 1

What Are Matter In Our Surroundings?


Anything that occupies space and has mass is called Matter.

Physical Nature Of Matter

  • Matter is made up of particles.
  • The particles of matter are very small they are small beyond our imagination.

Characteristics Of Particles Of Matter

  • Particles of matter have space between them.
  • Particles of matter are continuously moving.
  • Particles of matter attract each other.

States Of Matter

  • There are three states of matter namely solid, liquid and gas.
  • The main difference between these states of matter are given below:

States Of Matter

Solid Liquid Gas
  • Definite shape
  • No definite shape
  • No definite shape
  • Distinct boundaries and fixed volume
  • Fixed volume
  • No fixed volume
  • Not compressible
  • Can be compressible
  • Highly compressible
  • Cannot flow
  • Can flow
  • Can flow
  • Very less inter-particle space
  • Inter-particle spaces are more than in solids
  • Large inter-particle space is available
  • Maximum density
  • Density is between that of the solids and gases
  • Minimum density
  • Negligible rate of diffusion
  • Density is between that of the solids and gases
  • Maximum rate of diffusion
  • Inter-particle attraction is maximum
  • Rate of diffusion depends on inter-particle attraction
  • Inter-particle attraction is minimum
  • Inter-particle attraction is medium

Effect Of Temperature

  • The temperature at which a solid melts to become a liquid at the atmospheric pressure is called its melting point.
  • The temperature at which a liquid starts boiling at the atmospheric pressure is known as its boiling point. Boiling is a bulk phenomenon.
  • The phase change phenomenon where the substance is transformed form liquid state to solid state is known  as freezing point.
  • The phenomenon of changing of a liquid into its vapour state at any temperature below its boiling point is called evaporation. Evaporation is a surface phenomenon.

Factors affecting Evaporation

  1. An increase in surface area increases evaporation.
  2. An increase in temperature increases the rate of evaporation.
  3. A decrease in humidity increases the rate of evaporation.
  4. An increase in wind speed increases the rate of evaporation.
  5. Evaporation causes cooling effect.
  • The change of the state of matter from the gas phase into liquid is known as condensation, it is reverse of evaporation.
  • A change of state directly from solid to gas without changing into liquid state (or vice versa) is called sublimation.
  • The phase change from the gaseous state to a solid state, without passing through the liquid state, is called deposition or re-sublimation.

Some Measurable Quantities and there Units

Quantity Unit Symbol
Temperature Kelvin K
Length Metre m
Mass Kilogram Kg
Weight Newton N
Volume Cubic metre m3
Density Kilogram per cubic metre Kg/m3
Pressure Pascal Pa