# Matter in Our Surroundings Class 9 Notes Science - Chapter 1

## Matter

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