Chapter 1 Matter in Our Surroundings Class 9 Notes | EduRev

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Class 9 : Chapter 1 Matter in Our Surroundings Class 9 Notes | EduRev

 Page 1


Chapter 1 Matter in Our Surroundings 
Matter –Anything that occupies space and has mass is called matter. Literally everything around us is matter. 
Matter is made up of minute particles (smaller than we can even imagine). For example, a salt or sugar crystal is made of 
millions of smaller crystals that spread evenly when it is dissolved in water. 
Properties of particles of matter 
1. Particles of matter have spaces among them. (intermolecular spaces) 
2. They are continuously moving or they possess kinetic energy, which increases with increase in temperature. 
3. These particles attract each other. (intermolecular forces) 
Intermolecular – inter means between molecular means molecules. 
States of matter 
Various forms in which matter can exist 
1. Solids 
? Have definite shape and volume 
? Particles of solids have high intermolecular forces. 
? Particles of solids are packed tightly and have very less intermolecular spaces among them. They have the 
highest density 
? Solids cannot flow. 
? Particles of solids have very less kinetic energy. 
 
2. Liquids 
? Have definite volume but takes the shape of the container in which they are present. 
? Particles have intermediate intermolecular forces among them. 
? Particles are packed loosely and have more intermolecular forces than solids. Liquids have intermediate 
density. 
? Liquids can flow from high altitude to lower altitude. 
? Particles of liquids have more kinetic energy than the solids. 
 
3. Gases   
? Do not have definite shape or volume. 
? Particles have very less intermolecular forces among them. 
? Intermolecular spaces are large and therefore gases have very low density. 
? Gases can flow from a region of high concentration (where there is more gas) to a region of low 
concentration (where there is less gas).  
? The particles of gases move randomly at very high speed and therefore has the highest amount of kinetic 
energy. 
? Gases can be compressed by applying pressure as they have large intermolecular spaces among their 
particles. E.g. CNG filled in cylinders. 
Melting or Fusion – The process of conversion of solid into liquid on increasing the temperature is called melting. 
Boiling or Vaporization – The temperature at which a liquid starts boiling or converting into vapors is known as boiling. 
Melting Point – the temperature at which a solid melt to form liquid at atmospheric pressure is called its melting 
temperature. E.g. the melting temperature of water is 0
0
C or 273.16K 
 
Boiling point – the temperature at which a liquid starts boiling (converting into gas or vapor) is known as its boiling 
temperature. E.g. the boiling point of water is 100
0
C or 373.16K 
Page 2


Chapter 1 Matter in Our Surroundings 
Matter –Anything that occupies space and has mass is called matter. Literally everything around us is matter. 
Matter is made up of minute particles (smaller than we can even imagine). For example, a salt or sugar crystal is made of 
millions of smaller crystals that spread evenly when it is dissolved in water. 
Properties of particles of matter 
1. Particles of matter have spaces among them. (intermolecular spaces) 
2. They are continuously moving or they possess kinetic energy, which increases with increase in temperature. 
3. These particles attract each other. (intermolecular forces) 
Intermolecular – inter means between molecular means molecules. 
States of matter 
Various forms in which matter can exist 
1. Solids 
? Have definite shape and volume 
? Particles of solids have high intermolecular forces. 
? Particles of solids are packed tightly and have very less intermolecular spaces among them. They have the 
highest density 
? Solids cannot flow. 
? Particles of solids have very less kinetic energy. 
 
2. Liquids 
? Have definite volume but takes the shape of the container in which they are present. 
? Particles have intermediate intermolecular forces among them. 
? Particles are packed loosely and have more intermolecular forces than solids. Liquids have intermediate 
density. 
? Liquids can flow from high altitude to lower altitude. 
? Particles of liquids have more kinetic energy than the solids. 
 
3. Gases   
? Do not have definite shape or volume. 
? Particles have very less intermolecular forces among them. 
? Intermolecular spaces are large and therefore gases have very low density. 
? Gases can flow from a region of high concentration (where there is more gas) to a region of low 
concentration (where there is less gas).  
? The particles of gases move randomly at very high speed and therefore has the highest amount of kinetic 
energy. 
? Gases can be compressed by applying pressure as they have large intermolecular spaces among their 
particles. E.g. CNG filled in cylinders. 
Melting or Fusion – The process of conversion of solid into liquid on increasing the temperature is called melting. 
Boiling or Vaporization – The temperature at which a liquid starts boiling or converting into vapors is known as boiling. 
Melting Point – the temperature at which a solid melt to form liquid at atmospheric pressure is called its melting 
temperature. E.g. the melting temperature of water is 0
0
C or 273.16K 
 
Boiling point – the temperature at which a liquid starts boiling (converting into gas or vapor) is known as its boiling 
temperature. E.g. the boiling point of water is 100
0
C or 373.16K 
 
Solidification – The process of conversion of liquid to solid by lowering the temperature or applying pressure is called 
solidification. E.g. Conversion of water to ice. 
Condensation – Conversion of gases to liquid by lowering the temperature or applying pressure is called condensation.  
Vapors appear on the outer surface of a glass containing ice cold water because the vapors present in the air condenses to 
for liquid state. 
Sublimation – The process in which a solid directly changes into gaseous form without the liquid stage is known as 
sublimation. E.g. Ammonium chloride, Camphor. 
 
Latent Heat of Vaporization – Amount of heat energy required to convert 1k of liquid into gas is called latent heat of 
vaporization. 
Latent Heat of Fusion – Amount of Heat required to convert 1kg of solid into liquid is called latent heat of fusion. 
 
Effect of Pressure on States of matter 
Pressure brings the particles of matter closer by applying force from outside. The gases, whose particles are very far away 
from each other come closer and converts to liquid. E.g. LPG cylinders in our houses contain gas in liquid form under 
high pressure. 
Heat or temperature on the other hands increases the kinetic energy of the particles and make them move away from each 
other. So, heat converts solids into liquids and liquids into gases by increasing the intermolecular space among them. 
 
Evaporation – The process of conversion of liquid present on the surface into vapors at any temperature less than the 
boiling point is known as evaporation. 
Evaporation occurs at any temperature (slow at lower temperatures and fast at higher temperatures) while boiling happens 
at or above boiling temperature. 
Evaporation occurs only at the surface while boiling happens throughout the liquid. 
Page 3


Chapter 1 Matter in Our Surroundings 
Matter –Anything that occupies space and has mass is called matter. Literally everything around us is matter. 
Matter is made up of minute particles (smaller than we can even imagine). For example, a salt or sugar crystal is made of 
millions of smaller crystals that spread evenly when it is dissolved in water. 
Properties of particles of matter 
1. Particles of matter have spaces among them. (intermolecular spaces) 
2. They are continuously moving or they possess kinetic energy, which increases with increase in temperature. 
3. These particles attract each other. (intermolecular forces) 
Intermolecular – inter means between molecular means molecules. 
States of matter 
Various forms in which matter can exist 
1. Solids 
? Have definite shape and volume 
? Particles of solids have high intermolecular forces. 
? Particles of solids are packed tightly and have very less intermolecular spaces among them. They have the 
highest density 
? Solids cannot flow. 
? Particles of solids have very less kinetic energy. 
 
2. Liquids 
? Have definite volume but takes the shape of the container in which they are present. 
? Particles have intermediate intermolecular forces among them. 
? Particles are packed loosely and have more intermolecular forces than solids. Liquids have intermediate 
density. 
? Liquids can flow from high altitude to lower altitude. 
? Particles of liquids have more kinetic energy than the solids. 
 
3. Gases   
? Do not have definite shape or volume. 
? Particles have very less intermolecular forces among them. 
? Intermolecular spaces are large and therefore gases have very low density. 
? Gases can flow from a region of high concentration (where there is more gas) to a region of low 
concentration (where there is less gas).  
? The particles of gases move randomly at very high speed and therefore has the highest amount of kinetic 
energy. 
? Gases can be compressed by applying pressure as they have large intermolecular spaces among their 
particles. E.g. CNG filled in cylinders. 
Melting or Fusion – The process of conversion of solid into liquid on increasing the temperature is called melting. 
Boiling or Vaporization – The temperature at which a liquid starts boiling or converting into vapors is known as boiling. 
Melting Point – the temperature at which a solid melt to form liquid at atmospheric pressure is called its melting 
temperature. E.g. the melting temperature of water is 0
0
C or 273.16K 
 
Boiling point – the temperature at which a liquid starts boiling (converting into gas or vapor) is known as its boiling 
temperature. E.g. the boiling point of water is 100
0
C or 373.16K 
 
Solidification – The process of conversion of liquid to solid by lowering the temperature or applying pressure is called 
solidification. E.g. Conversion of water to ice. 
Condensation – Conversion of gases to liquid by lowering the temperature or applying pressure is called condensation.  
Vapors appear on the outer surface of a glass containing ice cold water because the vapors present in the air condenses to 
for liquid state. 
Sublimation – The process in which a solid directly changes into gaseous form without the liquid stage is known as 
sublimation. E.g. Ammonium chloride, Camphor. 
 
Latent Heat of Vaporization – Amount of heat energy required to convert 1k of liquid into gas is called latent heat of 
vaporization. 
Latent Heat of Fusion – Amount of Heat required to convert 1kg of solid into liquid is called latent heat of fusion. 
 
Effect of Pressure on States of matter 
Pressure brings the particles of matter closer by applying force from outside. The gases, whose particles are very far away 
from each other come closer and converts to liquid. E.g. LPG cylinders in our houses contain gas in liquid form under 
high pressure. 
Heat or temperature on the other hands increases the kinetic energy of the particles and make them move away from each 
other. So, heat converts solids into liquids and liquids into gases by increasing the intermolecular space among them. 
 
Evaporation – The process of conversion of liquid present on the surface into vapors at any temperature less than the 
boiling point is known as evaporation. 
Evaporation occurs at any temperature (slow at lower temperatures and fast at higher temperatures) while boiling happens 
at or above boiling temperature. 
Evaporation occurs only at the surface while boiling happens throughout the liquid. 
 
Factors effecting evaporation  
1. Temperature – Rate of evaporation increases with rise in temperature. 
2. Wind speed – Higher the wind speed, higher is the rate of evaporation. 
3. Humidity – Humidity is the amount of water vapors in the air. Rate of evaporation decreases with increase in 
humidity. 
4. Surface area – evaporation increases with increase in surface area of the liquid that is exposed to the 
environment. 
What happens during evaporation? 
The water on the surface absorbs energy from the surroundings, increases their kinetic energy, overcome the force of 
attraction with the surrounding particles and converts to vapors. 
This reduces the heat energy in the surrounding as the heat is absorbed by the liquid on the surface to evaporate and the 
surrounding become cool. 
This the explains the phenomenon of cooling of body during sweating, cooling by a water cooler and cooling caused by 
sprinkling water in hot summers. 
 
Two newly discovered states of matter: 
1. Plasma – consist of charged gaseous particles that are highly energetic and excited. E.g. neon or helium gas in 
bulbs. 
2. Bose-Einstein Condensate – It is formed by cooling of a gas of extremely low density at super low temperature. 
 
*Read NCERT for activities and experiments. 
 
 
 
 
 
 
 
 
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