CBSE Class 9 Science Notes – Chapter 1 : Matter In Our Surroundings

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

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