Nature Of Matter Notes: Class 9 BOSEM

Nature of mater notes

Nature of Matter Notes for Class 9 is a comprehensive study guide that covers all the topics covered in your science textbook as per Board of Secondary Education Manipur(BOSEM) Chapter 1: Nature of Matter.

The notes are prepared for you in an easy-to-understand with animations wherever applicable. The notes provided below will help you understand the core concept of the nature of matter.

After studying the chapter you will have the concept of the following topics.

  • What is matter?
  • Classification of matter
  • States of Matter
  • Effects of temperature on different states of matter
  • Effects of pressure on different states of matter


The matter may be defined as anything that occupies space, has mass and can be felt by one or more of our senses.

Examples are Tables, books, chairs, plants, animals, etc.

We are surrounded by matters. Matters are made up of tiny particles.

Characteristics of particles of matter

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

Classification of matter

Matters can be classified into

  • Chemical Classification
  • Physical classification

Chemical Classification

Depending upon the nature of the components, we can classify matter into two types:

  1. Homogeneous matter: Matters which have uniform composition throughout. For Example salt solution.
  2. Heterogeneous matter: Matters consisting of two or more components which are unevenly distributed. For example: A mixture of oil and water, muddy river water.

Physical classification

Based on the physical characteristics, matter can be classified into three states i.e.,

  • Solids
  • Liquid
  • Gases

Properties of solids

  1. Solids have a fixed shape and definite volume
  2. The constituent particles of solids are closely packed
  3. Solids are incompressible
  4. Solids have high density and they do not diffuse.

Properties of Liquids

  1. Liquids do not have a fixed shape and take the shape of the container where they are put into
  2. They have fixed volume
  3. The constituent particles are loosely packed.
  4. Liquids are also incompressible
  5. Density is lower than solids and diffused.

Properties of Gases

  1. Gases have neither a fixed shape nor a fixed volume
  2. The constituent particles are free to move in all the surroundings
  3. They are highly compressible
  4. The distance between inner particles are largest
  5. they have very low density and are diffused.

Difference in the characteristics of states of matter

Definite shapeIndefinite shapeIndefinite shape
Definite volumeDefinite volumeIndefinite volume
Maximum force of attraction between particlesLess forces of attraction between particles as compared to solidNegligible force of attraction between particles
Have negligible compressibilitySlightly compressibleCan be compressed easily
The kinetic energy of particles is minimumThe kinetic energy of particles is more than solidThe kinetic energy of particles is maximum
Particles cannot move rather they vibrate only at their fixed positionsParticles can slide over one anotherParticles can move freely
Solids have the highest densityDensity is lower than solidGases have the lowest density
Solids cannot flowLiquids flow easilyGases flow easily

Interchanges in the state of matter

Matter can change its state from one form to another. For example, water can exist in three states of matter.

  • Solids in the form of ice
  • Liquids in the form of water
  • Gas as water vapour (steam)

Fig: Diagram showing inter-conversion of solids, liquids and gases

Matter can change its state by changing temperature and or by changing the pressure

Effects of temperature

  1. Solid to Liquid

On increasing the temperature of solids, the kinetic energy of the particles increases which overcomes the force of attraction between the particles thereby solid melts and is converted to a liquid. The process of melting, that is, the change of a solid state into a liquid state is known as fusion.

The fixed temperature at which a solid melts to become a liquid at the atmospheric pressure is called melting point.

The melting point of ice is 0°C (273.16 K 273 K)

2. Liquid to Gaseous

On increasing the temperature of liquids, particles start moving even faster thereby breaking the force of attraction between the particles and the liquid starts changing into gas. The process of changing of liquid state into a gaseous state at boiling point is called vaporization.

The temperature at which a liquid starts boiling at the atmospheric pressure is called boiling point.

The boiling point of water is 100°C (373K)

Latent heat: The hidden heat which breaks the force of attraction between the molecules during the change of state is called latent heat.

Latent heat of fusion: The amount of heat energy required to change 1kg of solid into liquid at its melting point.

Latent heat of vapourisation: The quantity of heat required to change 1kg of the liquid to vapour at its boiling point.

3. Solid to Gaseous


The process of changing a solid directly into the gaseous state on heating without changing into a liquid state and of vapours into a solid on cooling is called sublimation.

The solid particles formed when the gaseous state of a substance directly changes into the solid state is called sublimate. The common substance which undergoes sublimation is Iodine, Camphor, Naphthalene and Anthracene.


We can infer that the state of matter can be changed into another state by changing the temperature. Normally, a solid on heating changes into a liquid state. The liquid on further heating changes into the gaseous state. The reverse happens when the gaseous state is cooled. However, there are solids which on heating directly change into a gaseous state, without changing into a liquid state and vice versa.

Effect Of Pressure

Increasing or decreasing the pressure can change the state of matter. Applying high pressure and lowering the temperature can liquefy gases.

Solid carbon dioxide is stored under high pressure. It gets converted directly into the gaseous state on decreasing pressure to atmospheric pressure without coming into a liquid state. For this reason, solid carbon dioxide is known as dry ice.


The phenomenon of change of a liquid into vapours below its boiling point is called evaporation.

Factors affecting evaporation

  1. Surface area: The rate of evaporation increases with an increase in surface area
  2. Temperature: The rate of evaporation of a liquid increases with rise in temperature
  3. Humidity: The rate of evaporation decreases when humidity is high and vice versa
  4. Wind speed: Higher the wind speed the higher the rate of evaporation.

Evaporation causes cooling

In an open vessel, the liquids keep on evaporating. The particles of liquid absorb energy from the surroundings to regain the energy lost during evaporation. This absorption of energy from the surroundings makes the surroundings cold.

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