Matter in Our Surroundings Class 9 Notes Science Chapter-1

CBSE Class 9 Science Notes Chapter-1 Matter in Our Surroundings

CBSE Class 9 Science Chemistry Notes Chapter-1:- Here we have provided a summary and revision  Matter in Our Surroundings Class 9 Notes Science Chapter 1. Chemistry notes for class 9 chapter 1 is the first beginning and important chapter for the students. Students can also download chapter 1 in pdf form matter in our surroundings class 9 pdf at careerkhojo. For Revision work, you can find complete notes of the Chapter 1 Matter in Our Surroundings CBSE class 9 notes from here. It covers the main topic of CBSE Class 9 Science notes of chapter 1. NCERT Class 9 science chapter 1 notes

Class 9 Notes Science Chapter-1 (Matter around us class 9 notes)

Matter in Our Surrounding


From the very beginning, humans have been trying to understand the environment around them. And early Indian philosophers classified the postulates of matter.

According to the early Indian philosopher, every biotic and non-biotic thing made of five fundamental elements called Panchtatva. (Air, Water, Fire, Sky, Earth)

 chemistry notes for class 9 chapter 1


What Is Matter?

Any object or substance found in the universe, which has the ability to occupy space and has a mass, is called Matter.
For example:- Chair, Table, Honey, Oil, Perfume, Clouds, Star, Planets, etc.

Characteristics of Particles of Matter

In all phases, particles of matter have some of the following characteristics.

➢ There is space between Particles of Matter

For example:- Whenever we make tea, coffee, or lemon juice, the sugar particles completely dissolve in the water. This means that a particle of one substance gets into the empty space between particles of another substance.

➢ There is an attraction between the Particles of the Matter.

For example:- Everything we see around us has its own shape or size. This means that in order to maintain their shape, particles of matter are bonded to each other by an internal force. And the behavior of that internal force has attractive nature between the particles due to which the particles keep together.

➢ Particles of Matter move continuously.

For example:-Whenever two liquids are mixed, their particles intermix on their own with each other. 
Due to the diffusion process, the aroma of the perfume particles moves from one place to another. This means that particles have kinetic energy and they move randomly.

Type of States of Matter

There are mainly three types of Matters.

    • Solid,
    • Liquid,
    • Gas.

In addition, the other types of matter found in some other special conditions are as follows.

  • Plasma state
  • Bose-Einstein Condensate

Properties of three common State of Matters.

Properties of Solid State:-

➢ It has a fixed shape or size & definite volume.

➢ The particles of solid objects are very closely packed, due to which the attraction force between their molecules is very high.

➣ Solid objects have negligible properties of compressibility.

➣ Solid objects have very high Density, Boiling points, and Melting points.

➢ The intermolecular force between the particles is very high.

➢ Particles of solid objects are arranged in an order, due to which their shape is fixed, and hence the kinetic energy of the particles is very less.

➣ Solids have no flowing properties.

Properties of Liquid State:-

➢ Liquids have a definite volume.

Liquids do not have a fixed shape.

➣ The intermolecular force between the liquid particles is weaker than that of the solid particles.

➣ Liquid has almost incompressible.

➢ A liquid has a lower density, boiling point, and melting point than a solid.

➢ The inter-molecular force between liquid particles is less than that of solid.

➣ Liquid particles are arranged slightly away, so their kinetic energy is higher than the particles of solid objects.

➢ liquids can flow.

Properties of Gaseous State:-

➢ No definite shape & volume.

➢ Since their particles are far away, so the intermolecular force acting between the particles of the gas is very weak.

➣ The arrangement of gas particles is irregular.

➣ The density of gases is very low.

➢ Gases are highly compressible.

➢ Gases can flow.

Can Matter Change its State?

As we know that there are three states of matter i.e. Solid, Liquid & Gas. But the question is whether these three states can interchange with each other.
If we talk about the state of water, then it can exist in all three states of matter.

  • Solid- In Ice form
  • Liquid- In water form
  • Gas- In water vapor form

Since water can exist in three states, therefore, we can interchange the state of water by changing temperature and pressure.

1.) Effect of change of Temperature

Changes in the state of a matter can be made in two ways by increasing or lowering the temperature.

A) On increasing Temperature (Heating):-

When we change the state of a substance by increasing the temperature, the following events occur.

➢ As the temperature increases, the particles of matter get heat energy and as a result, the kinetic energy of the particles starts increasing.

➢ As the kinetic energy of the particles of matter increases, the molecular force inside them starts decreasing.

➣ Due to the decrease in the intermolecular forces between the particles, the particles of matter start to move irregularly.

➣ Thus the phase of the matter changes at a certain high temperature.

Solid to liquid conversion (Melting)

When the matter changes from solid to liquid (phase change), the temperature remains constant. Since the temperature remains constant as the phase changes, the given heat is used to break the intermolecular forces between the particles. For Example: (Ice to Water)

The following conditions occur during phase change.

Latent Heat:- 

The Heat energy absorbed or released by a substance during the phase transformation without changing its temperature is called LATENT HEAT.

Latent Heat of Fusion:- 

This is the amount of heat required to convert 1 KG of a solid mass into a liquid without the rise in temperature at atmospheric pressure.

Melting Point:- 

“The Melting point of a solid is defined as the temperature at which the solid melts and becomes liquid at Atmospheric Pressure.”
The melting point of different solids is different. If we talk about the Melting point of ice, then this value is 273.16 kelvin.

Liquid to Vapour conversion (vaporization)

To convert a liquid to vapor, the intermolecular force between the particles of the liquid has to be broken by supplying heat. And then it changes from liquid to vapor at a specific temperature.

Boiling Point:-  

This is the temperature at which the liquid starts boiling atmospheric pressure. This is possible only when the vapor pressure is equal to the atmospheric pressure.

So, the Boiling point of a liquid is the temperature at which the vapor pressure of the liquid becomes equal to the atmospheric pressure.

Latent Heat of Vaporisation:- 

The amount of heat energy required to convert 1 KG of a liquid into vapor without the rise in temperature at atmospheric pressure.

Solid to Vapor conversion (Sublimation)

There are also some substances that, when heated, turn directly from solid to vapor state. For Example: Camphor


The process of changing the solid phase to the gaseous phase directly (or vice versa) without converting it into a liquid phase is called Sublimation.

B) On Decreasing Temperature (Cooling):-
Vapor to liquid conversion (Condensation)

When the given latent heat of evaporation is extracted from or extracted from gaseous or water vapor, it is converted into a liquid. This process is called condensation.

In simple language, it can be defined as—

“The process of converting a gaseous phase into a liquid phase at a particular temperature is known as Condensation.”

For example:- Rainfall (precipitation) from the cloud is formed by the condensation process.

Liquid to Solid conversion (Solidification)

“The process of converting a liquid phase into a solid phase at a particular temperature is known as solidification.” This process is also known as the freezing process. 
The Freezing process is the opposite of the Fusion or Melting process.

For Example: Since it is an exothermic process (Heat release), the process of making ice from water is a freezing process.

Gaseous to Solid conversion ( Desublimation or Deposition)

“The process of changing the gaseous phase to the solid phase directly (or vice versa) without converting it into a liquid phase is called Desublimation or Deposition.”

2.) Effect of change of Pressure

The effect of pressure changes is not seen in solids and liquids because the properties of compressibility are negligible in them. Since gases are highly compressible, so the gases show the effect of change of pressure.

➣ In the case of gases, “Gases can be converted into a liquid by applying high pressure and lowering the temperature.”

➢ At high pressure, the particles are attracted to each other and bond with molecular forces. Due to which the gaseous state changes into a liquid.

For example-

  • An LPG gas cylinder,
  • Solid carbon-dioxide is stored under high pressure which liquefies quickly as soon as the pressure is reduced to 1 atmospheric pressure.


What is Evaporation?

“The process in which liquid changes into water vapors below its boiling point at any temperature is called evaporation. It is a surface phenomenon.”

Factors affecting Evaporation:-

The following factors affect the rate of evaporation.

1. Temperature:- The rate of evaporation increases with an increase in temperature. So that the particles get enough kinetic energy to escape into the vapor state.

2. Surface Area:- Since evaporation is a surface area phenomenon, the rate of evaporation increases as the surface area increases.

3. Humidity:- The amount of water vapor contains in the atmospheric air is known as Humidity. And the rate of evaporation is inversely proportional to Humidity. Therefore, when the humidity in the air increases, the rate of evaporation will decrease.

3. Wind Speed:- As you may have noticed that wet clothes dry quickly due to strong winds. This means that the evaporation rate increases as the wind speed increases.


Leave a Comment