Class 9 Science Chapter 1 Matter in Our Surroundings Notes

9 Class Science Chapter 1 Matter in Our Surroundings Notes

TextbookNCERT
ClassClass 9
SubjectScience
Chapter Chapter 1
Chapter NameMatter in Our Surroundings
CategoryClass 9 Science Notes
MediumEnglish

Class 9 Science Chapter 1 Matter in Our Surroundings Notes. here we will be learn about Matter , Particle nature of matter , All five states of matter & their behaviour , Enter conversion of states of matter , Evaporation & Boiling , Conversion between Kelvin scale & Celsius scale etc.

Class 9 Science Chapter 1 Matter in Our Surroundings Notes

📚 Chapter = 1 📚
💠 Matter in Our Surroundings 💠

💠 Topics in the Chapter :-

  • Matter
  • Particle nature of matter. 
  • All five states of matter & their behaviour 
  • Enter conversion of states of matter 
  • Evaporation & Boiling
  • Conversion between Kelvin scale & Celsius scale

❇️ Matter :-

🔹 The matter is the material of which everything in this universe, (in and around us) is made up of. It is anything that occupies space and has mass and offers resistance to any applied force.

❇️ Physical Nature of Particles :-

  • Matter is made up of particles. 
  • The particles of matter are very-very small. they are small beyond Our imagination.

❇️ Characteristics of Particles :-

🔶 Particles of matter are continuously moving. 

  • i.e :- they possess kinetic energy. As the temperature rises, particles moves faster because kinetic energy of the particles increases.

🔶 Particles of matter have space between them. 

  • Example :- When we make tea, coffee or lemonade (nimbu pani), particles of one type of matter get into the space between particles of the other. This shows that there is enough space between particles of matter. 

🔶 Particles of matter attract each other. 

  • Example :- When we open a water tap, try to break the stream of water with out fingers, can we do this ? No, because the stream of water remains together. Particles of water are held together because of the force of attraction between them.

🔹The space between the particles and kinetic energy of particles is minimum in solids, intermediate in liquids and maximum in gases. 

🔹The force of attraction between the particles is strongest in solids, intermediate in liquids and weakest in gases.

🔹Movement of particles is minimum in solids, more in liquids and maximum in gases.

❇️ States of Matter :-

🔹 The physical states of a matter are : 

  • ( i ) Solid, 
  • ( ii ) Liquid,
  • ( iii ) Gas. 

🔹 We can classify our body into three states of matter i.e.:-

  • Bones and teeth are solids.
  • Blood and water present in our body are liquids. 
  • Air in our lungs is gaseous.

❇️ ( i ) Solid State :-

🔶 Characteristics of solid states are :-

  • Have definite shape. Fixed mass, volume and shape.
  • Have distinct boundaries. 
  • Inter-particle distances are least. 
  • Have rigidity and incompressibility. 
  • Have definite volume.
  • High density and do not diffuse. 
  • Inter particle forces of attraction are strongest. 
  • Constituent particles are very closely packed. 

🔶 Macroscopic Explanation for Properties of solids :-   

🔹Solids have a definite shape and a definite volume because the particles are locked into place. 

🔹Solids do not flow easily because the particles cannot move/slide past one another. 

🔹Solids are not easily compressible because there is little free space between particles. 

❇️ ( ii ) Liquid State :-

🔶 The characteristics of liquid state are :-

  • Have fluidity i.e., they are not rigid. 
  • Low compressibility. 
  • No definite shape and boundaries. They take the shape of the vessels. 
  • Have definite volume. 

🔶 Microscopic Explanation for Properties of Liquids :-

🔹 Liquids are substances having fixed (definite) volume and no fixed shape. They take the shape of the container in which they are stored. 

🔹 Force of attraction between the particles of liquid keeps its volume same. 

🔹 Diffusion is much more in liquids than in solids due to free movement of particles of liquids.

❇️ ( iii ) Gaseous State :-

🔶 The characteristics of gaseous state are :-

  • Have fluidity. 
  • Have high compressibility. 
  • Have no definite boundaries. 
  • Have no definite shape. 
  • Have no definite volume. 

🔶 Microscopic Explanation for Properties of Gases :-

🔹 Gases are substance that do not have fixed volume and occupy all the volume available to them.

🔹 The gases (oxygen and carbon dioxide) from the atmosphere diffuse and dissolve in water. Due to these gases aquatic plants and animals are able to survive. 

🔹 The particles in a gas are free to move in any direction hence gases can flow. 

🔹 Pressure of gas is the force applied on the walls of vessel by the irregular moving gas particles.

❇️ Change of State of Matter :-

🔹 Water can exist in three states of matter i.e., 

  • solid – ice, 
  • liquid – water, 
  • gas – water vapour. 

🔹 On heating ice melts into water and then converts into water vapours.


❇️ How Change in the physical state of matter ?

🔹 Change in the physical state of matter can be done in two ways :-

  • By Changing the Temperature
  • Effect of Change of Pressure

❇️ By Changing the Temperature :-

🔶 ( i ) Melting Point :-

🔹 The temperature at which a solid melts to form liquid at atmospheric pressure is called its melting point. 

  • Melting point of ice is 273.16 K (0°C). During melting the temperature of ice does not rise even though heat is being supplied continuously because of latent heat of fusion. 
  • This latent heat of fusion is used up to overcome the forces of attraction between ice particles. At 0° C energy of water particles is much more than the energy of particles of ice at 0°C.

🔶 ( ii ) Boiling Point :-

🔹 The temperature at which a liquid boils to form vapours at atmospheric pressure is called its boiling point. Boiling point of water is 373 K (100°C+273 = 373 K).

  • During boiling the temperature of water does not rise even though heat is being supplied continuously as this heat of vapourization is used up to overcome the forces of attraction between water particles.
  • At 100°C, energy of water vapours is much more than the energy of water at 100°C. So, we can change one state of matter to another state by changing temperature.

🔶 ( iii ) Sublimation :-

🔹The change of solid directly into vapours on heating and of vapours into solid on cooling without passing through the intervening liquid state is called sublimation. 

🔹 Example :- When camphor or ammonium chloride is heated in a China dish covered by a inverted funnel (with cotton plug in its upper open end), the vapours of ammonium chloride are converted into solid ammonium chloride on coming in contact with the cold inner walls of the funnel.

❇️ Effect of Change of Pressure :-

  • If we compress a gas in a cylinder, the distance between the particles of gas is reduced and finally gas is liquefied on lowering temperature.
  • By applying high pressure, the particles of a gas can be brought close together. 
  • Solid carbon dioxide (dry ice) is changed into carbon dioxide gas directly without changing into liquid when pressure is reduced to one atmospheric pressure.

🔹 Thus, states of matter i.e., solid, liquid and gas are determined by temperature & pressure. 


❇️ Latent Heat of Fusion :-

🔹 The amount of heat required to change 1 kg solid to its liquid state (at its melting point) at atmospheric pressure. 

❇️ Latent Heat of Vapourization :-

🔹 The amount of heat required to change 1 kg liquid to its gaseous state (at its boiling point) at atmospheric pressure. 

❇️ Evaporation :-

🔹 A surface phenomenon in which liquid changes into vapours at any temperature below its boiling point is called evaporation. 

🔹 Particles on the surface of a liquid have higher kinetic energy than others, so they break the forces of attraction between the particles & escape from the surface of liquid in the form of vapours. 

❇️ Factors affecting evaporation :-

🔹 Rate of evaporation depends on :-

🔶 Exposed surface area :- On increasing surface area of liquid, rate of evaporation increases. 

🔶 Increase in temperature :- Increases kinetic energy of particles hence rate of evaporation increases. 

🔶 Humidity :- When the humidity of air (degree of dampness of air) is low, evaporation rate is increased. More humidity, less evaporation. 

🔶 Wind :- When wind speed increases, rate of evaporation also increases.

❇️ Evaporation always causes cooling why ?

🔹 The cooling caused by evaporation is based on the fact that when a liquid evaporates, it takes latent heat of vaporization from surroundings which on losing heat get cooled.

❇️ Different between Evaporation and Boiling  :-

EvaporationBoiling
Evaporation is a surface phenomenon.Boiling is a bulk phenomenon. 
Particles from the surface gain enough energy to overcome the forces of attraction present in the liquid and change into the vapour state. Particles from the bulk (whole) of the liquid change into vapour state.

❇️ PLASMA (NON-EVALUATIVE) :-

🔶 Characteristics of PLASMA are :-

  • A plasma is an ionized gas. 
  • A plasma is a very good conductor of electricity and is affected by magnetic fields. 
  • Plasma, like gases have an indefinite shape and an indefinite volume. Ex. lonized gas 

🔶 Microscopic Explanation for Properties of Plasmas :-    

🔹Plasmas have an indefinite shape and an indefinite volume because the particles can move past one another. 

🔹Plasmas are easily compressible because there is a great deal of free space between particles. 

🔹Plasmas are good conductors of electricity &are affected by magnetic fields because they are composed of lens. 

❇️ BOSE-EINSTEIN CONDENSATE (non – evaluative)  :-

🔶 Characteristics of BOSE-EINSTEIN CONDENSATE are :-

  • A BEC is a state of matter that can arise at very low temperatures. 
  • The scientists who worked with the Bose- Einstein condensate received a Nobel Prize for their work in 1995. 
  • The BEC is all about molecules that are really close to each other (even closer than atoms in a solid).

🔶 Microscopic Explanation for Properties of BEC :-    

🔹Particles are less energetic than solids because Exist at very low temperature. 

🔹Particles are literally indistinguishable because they are locked into same space. 

🔹BEC shows super fluidity because Particles can flow without friction.

❇️ Some Important Measurements :-

🔹Sl unit of temperature is Kelvin. T (K) = T(‘C) + 273 

🔹Kelvin is the Sl unit of temperature, 0°C = 273.16 K we take 0°C = 273 K. 

🔹Kelvin scale of temperature has always positive sign , hence regarded as better scale than Celsius. 

🔹Atmosphere (atm) is a unit of measuring pressure exerted by a gas. The SI unit of pressure is Pascal (Pa):

🔹1 atmosphere = 1.01 x (10 to the power 5) Pa. 

🔹 The pressure of air in atmosphere is called atmospheric pressure. The atmospheric pressure at sea level is 1 atmosphere, and is taken as the normal atmospheric pressure.

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