Matter In Our Surroundings Class 9 Notes - Chapter 1

CBSE Class 9 Science Notes Chapter 1 Matter In Our Surroundings

Download PDF Download PDF

Anything that has mass and takes up space is referred to as matter. hydrogen and oxygen, sugar and sand, air and water, etc. Small, minuscule particles make up matter. Due to the space between them, matter particles are attracted to one another.

States of Matter

  • Matter can be classified as solid, liquid or gas on the basis of interparticle forces and the arrangement of particles.
  • These three forms of matter are interconvertible by increasing or decreasing pressure and temperature.  For example, ice can be converted from solid to a liquid by increasing the temperature.

For more information on Matter Around Us, watch the below video

To know more about the States of Matter, visit here.

Property  Solid Liquid Gas
Shape and volume Fixed shape and volume No fixed shape but has volume Neither definite shape nor volume
Energy Lowest Medium Highest
Compressibility Difficult Nearly difficult Easy
Arrangement of molecules Regular and closely arranged Random and little sparsely arranged Random and more sparsely arranged
Fluidity Cannot flow Flows from higher to lower level Flows in all directions
Movement Negligible Depends on interparticle attraction Free, constant and random
Interparticle space Very less More Large
Interparticle attraction Maximum Medium Minimum
Density Maximum Medium Minimum
Rate of diffusion Negligible It depends on interparticle attraction. Maximum

For more information on the States of Matter, watch the below video

Atomic View of the Three States of Matter

solids structure
liquids structure
Gas molecules

Physical Nature of Matter

  • A physical property is an aspect of matter that can be observed or measured without changing its nature or composition.
  • It is independent of the amount of matter present.
  • Physical properties include appearance, colour, odour, density, texture, melting point, boiling point, solubility, etc.

For more information on Physical Nature of Matter, watch the below video

To know more about the Physical Nature of Matter, visit here.

Characteristics of Particles of Matter


Matter is anything that has mass and occupies space.

  • Everything that we can touch, see, hear, taste and also smell is matter.
  • It is made up of really tiny particles which cannot be seen through the eye.

For more information on Characteristics of Particles of Matter, watch the below video

The particles of which the matter is comprised influence its state and properties (physical and chemical).

1. Particles of matter have spaces between them

  • This characteristic is one of the concepts behind the solubility of a substance in other substances. For example, on dissolving sugar in water, there is no rise in the water level because the particles of sugar get into the interparticle spaces between the water particles.

2. Particles of matter are always in motion

  • Particles of matter show continuous random movements due to the kinetic energy they possess.
  • A rise in temperature increases the kinetic energy of the particles, making them move more vigorously.

3. Particles of matter attract each other
In every substance, there is an interparticle force of attraction acting between the particles. To break a substance, we need to overcome this force. The strength of the force differs from one substance to another.

To know more about the Characteristics of Particles of Matter, visit here.


When the particles of matter intermix on their own with each other, the phenomenon is called diffusion. For example, spreading of ink in water.

  • During diffusion, the particles occupy the interparticle spaces.
  • The rate of diffusion increases with an increase in temperature due to increase in the kinetic energy of the particles.

To know more about Diffusion, visit here.

Can Matter Change Its State?

Effect of Change of Temperature on the State of Matter

On increasing the temperature, the kinetic energy of the particles of the matter increases, and they begin to vibrate with higher energy. Therefore, the interparticle force of attraction between the particles reduces, and particles get detached from their position and begin to move freely.

  • As a result, the state of matter begins to change.
  • Solids undergo a phase change to form liquids.
  • Similarly, liquids also undergo a phase change to form gases.

To know more about the Changing State of Matter, visit here.

Melting Point

The melting point of a solid is defined as the temperature at which solid melts to become liquid at the atmospheric pressure.

  • At the melting point, these two phases, i.e., solid and liquid, are in equilibrium, i.e., at this point, both solid state and liquid state exist simultaneously.


When two atoms collide to create a heavier atom, such as when two hydrogen atoms combine to create one helium atom, this process is known as fusion. This process generates enormous amounts of energy, many times more than fission, and powers the sun. Furthermore, it doesn’t generate radioactive fission products.

The melting point at which ice, a solid, turns to water, a liquid, is 32°F (0°C).

Boiling Point

The boiling point of a liquid is defined as the temperature at which the vapour pressure of the liquid is equal to the atmospheric pressure.

The boiling point for any material is the temperature point at which the material transforms into the gas phase in the liquid phase. This happens at 100 degrees centigrade for water. The Celsius scale was in fact created on the basis of the ice/water melting point and the liquid water/vapor boiling point.

Read more: Celsius to Kelvin

Latent Heat of Fusion

It is the amount of heat energy that is required to change 1 kg of a solid into liquid at atmospheric pressure at its melting point.

Latent Heat of Vaporisation

It is the amount of heat energy that is required to change 1 kg of a liquid into gas at atmospheric pressure at its boiling point.


The transition of a substance directly from its solid phase to gaseous phase without changing into the liquid phase (or vice versa) is called sublimation.

Sublimation – Solid to Gas Phase Transformation

Effect of Change in Pressure on the State of Matter

By applying pressure, the interparticle spaces between particles of matter decrease. Thus, by applying pressure and reducing temperature, we can convert a solid to liquid and a liquid to gas.

Flowchart for Inter-Conversion of the Three States of Matter

Changing States Of Matter


The phenomenon by which molecules in liquid state undergo a spontaneous transition to the gaseous phase at any temperature below its boiling point is called evaporation.

  • For example, the gradual drying of damp clothes is caused by the evaporation of water to water vapour.

For more information on Evaporation, watch the below video

To know more about Evaporation, visit here.

Factors Affecting Evaporation

  • Temperature: The rate of evaporation increases with an increase in temperature.
  • Surface area: The rate of evaporation increases with an increase in surface area.
  • Humidity: The rate of evaporation decreases with an increase in humidity.
  • Wind speed: The rate of evaporation increases with an increase in wind speed.

To know more about Factors Affecting Rate of Evaporation, visit here.

Cooling Due to Evaporation

During evaporation, the particles of a liquid absorb energy from the surroundings to overcome the inter-particle forces of attraction and undergo phase change. The absorption of heat from the surrounding makes the surroundings cool.

For example, sweating cools down our body.

Applications of Evaporative Cooling

  • To keep water cool, it is kept in earthenware containers. Similar to the pores in cotton fabric, the pores in the earthen pot’s surface area allow for more evaporation.
  • To keep our bodies cool, we sweat a lot. Evaporation is what transpiration ultimately is. Our body’s water evaporates, using energy in the process and lowering our body temperature as a result.
  • We dress in cotton during the summer. Since cotton is a powerful water absorbent, it allows more perspiration to come into touch with the air, promoting more evaporation. We have a cooling effect when wearing cotton clothing because of this.

Read More:

Frequently Asked Questions on CBSE Class 9 Biology Notes Chapter 1 Matter in Our Surroundings


What is the ‘latent heat of fusion’?

The latent heat of fusion is the enthalpy change of any amount of substance when it melts.


What does ‘sublimation critical point’ mean?

The sublimation critical point refers to the maximum or minimum temperature and pressure beyond which the state of the matter cannot be changed.


What does ‘interconversion of matter’ mean?

Interconversion of matter refers to the change from one state to another. It is a process by which matter changes from one state to another and back to its original state without any change in its chemical composition.


Leave a Comment

Your Mobile number and Email id will not be published.



Tuition Center
Tuition Centre
free trial
Free Trial Class
Scholarship Test
Scholarship Test
Question and Answer
Question & Answer