CLASS 9

1. GRADE 9
SCIENCE
CHAPTER – 1
MATTER IN OUR SURROUNDINGS
part-2

2. MATTER
• Matter is anything that has mass and volume.
• Anything that occupies space and can be felt by our one or more
sense organs is called matter.

3. Classification of Matter
• Indian philosophers classified matter into five basic elements.
Air
Water
Earth
Sky
Fire

4. Classification of Matter
• Based on physical nature, matter is divided into three types.
Solid
Liquid
Gas
• Based on chemical nature, matter is divided into three types.
Elements
Compounds
Mixtures

5. Physical nature of Matter
• Every matter is made up of certain particles which differ in shape, size
and nature from the other type of matter.
• The particles of matter are very small beyond our imagination.

6. Characteristics of Particles of Matter
• Particles of matter are very small.
• Particles of matter have space between them
• Particles of matter are continuously moving.
• Particles of matter attract each other.
• Particles of matter diffuse with each other.

7. Diffusion
• Intermixing of particles of two different types of matter on their own
is called diffusion.
• Diffusion is a process in which molecules of a substance move from
higher concentration to lower concentration and goes on until a
uniform mixture is formed.
The rate of diffusion increases on heating, since increase in temperature
increases the kinetic energy of the particles and they move faster.
Diffusion is fastest in gases as the particles move rapidly. It is slowest in solids
as particles do not move much. Diffusion in liquids is faster than solids and
slower than gases.

8. Properties of Liquid State
• Liquids have fixed volume but no fixed shape, they take the shape of the
container.
• Liquids flow and change shape. So they are not rigid, but can be called
fluid.
• Solids, liquids and gases can diffuse into liquids.
• Liquids are almost incompressible.
• The attraction force between the liquid particles is greater than that of
gases, but less than that of solids.
• Density of liquid is less than that of solid.
• The rate of diffusion of liquids is higher than that of solids as liquid
particles can move freely.

9. Gaseous State
• Gases are highly compressible when compared to solids and liquids.
• Gases do not have definite shape and definite volume.
• Gases have mass and occupy the entire space available.
• Gases have a tendency to flow and hence they are called as fluids.
• They have high diffusing tendency into other gases.
• In gaseous state, the particles move about randomly at high speed.
• The density of gas is minimum. It is lighter than the same volume of solid
and liquid.
(Textbook)

10. Particle mode of three States
• Following properties of particles decide the state of matter:
Intermolecular distance
Force of attraction between the particles
Kinetic energy of the particles.

11. States of Matter on the basis of Molecular
Structure
• Solid state:
 Intermolecular spaces are very small
 Intermolecular force are very large
 Molecules can vibrate from their mean position but can not
change their position
 Therefore, solids have definite shape, definite volume and are
incompressible.

12. States of Matter on the basis of Molecular
Structure
• Liquid state:
 Intermolecular spaces are somewhat large
 Intermolecular forces are small as compared to solids
 Liquid molecules have more kinetic energy than solids
 Due to large intermolecular space and kinetic energy, the
molecules can interchange their positions
 Therefore, liquids take the shape of the container and flow from
higher level to lower level.

13. States of Matter on the basis of Molecular
Structure
• Gaseous state:
 Intermolecular spaces are 1000 times more than the liquids
 intermolecular forces are almost negligible
 The molecules are free to move in any direction
 Therefore gases have no definite shape or volume
 Kinetic energy of gases are maximum and they move randomly at
high speed
 Gas molecules hit the sides of the vessel and exert pressure on
the walls of the container.