Class 9 Science Chapter 1 Matter in our Surrounding Notes
WHAT IS MATTER ?
Anything that occupies space and has mass is called matter.
PHYSICAL NATURE OF MATTER:-
Matter is made up of tiny particles which cannot be seen through the eye..
HOW SMALL ARE THESE PARTICLES OF MATTER?
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.
Because of this characteristic the solubility of a substance in other substance is possible. For example, If we dissolve sugar in water it gets dissolve without any rise in water level because its particles get into the interparticle spaces between the water particles.
Particles of matter are continuously moving.
Due to the kinetic energy in the particles of matter it show continuous random movements.
As the temperature increases the kinetic energy of the particles also increases, which make them move more vigorously.
Particles of matter attract each other.
The particles of matter have interparticle force acting between them. This force keeps the particles together.
STATES OF MATTER:-
CAN MATTER CHANGE ITS STATE?
Yes, all three forms of matter are interconvertible by increasing or decreasing pressure and temperature.
EFFECT OF CHANGE OF TEMPERATURE
On increasing the heat, the particles of the matter gain kinetic energy and start vibrating. Due to this increased kinetic energy the particles overcome the force of attraction and a new state is obtained.
This inter mixing of particles of two different types of matter on their own is called diffusion. On heating, diffusion becomes faster.
The minimum 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.
LATENT HEAT OF FUSION
The amount of heat energy required to change 1 kg of a solid into liquid at its melting point is called the latent heat of fusion of the solid.
LATENT HEAT OF VAPORIZATION
The amount of heat energy required to change 1 kg of a liquid to vapour at atmospheric pressure, at its boiling point is called the latent heat of vaporization of the liquid.
A change of state directly from solid to gas without changing into liquid state (or vice versa) is called sublimation.
The process of melting, that is, change of solid state into liquid state is also known as fusion.
The phenomenon of changing of a liquid into vapours at any temperature below its boiling point is called evaporation.
FACTORS AFFECTING EVAPORATION
Temperature : With an increase in temperature the rate of evaporation increases.
Surface area: With an increase in surface area the rate of evaporation increases.
Humidity: With an increase in humidity the rate of evaporation decreases.
Wind speed: With an increase in wind speed the rate of evaporation increases.