'Matter Around Us' CBSE NCERT Class - 9th

1. MATTER AROUND US

2. WHAT IS MATTER ? Anything which occupy space and have mass is called Matter. For e.g., clouds, sand, air, wood, stars, plants, animals, etc. Everything in this universe is made up of ‘Matter’. • Early Indian Philosophers classified ‘Matter’ in the form of basic five elements – air, earth, fire, sky and water, together called ‘Panch Tatva’. According to them all the living and non – living things constituted of Panch Tatva. • Modern day scientists have evolved two types of classification of ‘Matter’ on the basis of their Physical Properties and Chemical Nature.

3. PHYSICAL NATURE OF MATTER The physical nature of matter depends on the basis of few characteristics such as:- • The Particles of Matter are very very small. • The Particles of Matter have space between them. • The Particles of Matter are continuously moving. • The Particles of Matter attract each other.

4. KINETIC ENERGY The Kinetic Energy of an object is the energy that it possesses due to its Motion. • Particles of Matter are continuously moving because they possess Kinetic Energy. As the temperature rises, particles start moving faster. So, with an increase in temperature leads to an increase in the kinetic energy of the particles.

5. DIFFUSION The spontaneous intermixing of particles of two different types of matter on their own is called Diffusion. When there is a rise in temperature (Heat), the rate of diffusion also increases. For e.g. :- 1. Aroma of hot sizzling food. 2. Smell of burning Incense stick. 3. Fragrance of perfume.

6. INTERMOLECULAR FORCE The Particles of Matter have force acting between them, which is called Intermolecular Force of Attraction. This force keeps the particles together. The Strength of this force of attraction varies from one kind of Matter to one another.

7. STATES OF MATTER Matter around us exists in the three different states – Solid, Liquid and Gaseous state. These states arises due to variation in the characteristics of Particles of Matter.

8. SOLID STATE The properties of a solid are: - • The molecules are very tightly packed and intermolecular force of attraction is very high in solids. • Solids have a definite shape, distinct boundaries and fixed volume. • They have tendency to maintain their shape and size unless and until an external force acts on them, that is why they are, rigid and hard. • Movement of particles is negligible and possess least Kinetic Energy. • Solids possess high density. • The rate of diffusion in solids is negligible. • Solids are negligible compressible.

9. LIQUID STATE The properties of Liquid State are: - • The molecules are loosely arranged and the intermolecular force of attraction is less in liquids than solids. • Liquids do not have fixed shape, but take the shape of the container in which they are kept and have fixed volume. • They have tendency to flow and are also called Fluids. • Movement of particles is higher and possess higher Kinetic Energy. • Liquids have low density. • The rate of diffusion is higher in liquids than that of solids. • Liquids are highly compressible.

10. GASEOUS STATE The properties of Gaseous State are: - • The molecules are very loosely packed and the intermolecular force or attraction is least in gases. • Gases do not have fixed shape take the shape of the container in which they are kept and do not have fixed volume. • Movement of particles is highest in gases and possess highest Kinetic Energy. • Gases possess low density • The rate of diffusion is highest in gases. • Gases are also highly compressible.

11. Difference Between the Properties of States of Matter

12. CAN MATTER CHANGE ITS STATES ? Matters can be changed from one state to another state. The change of state of matters depends upon mainly two factors: • Temperature – 1) Solids change into liquid with increase in temperature. (Solid → Liquid). 2) A liquid changes into gas by increase in temperature. (Liquid → Gas). 3) Gas changes into liquid by decrease in temperature. (Gas → Liquid). 4) Liquid changes into solid by decrease in temperature. (Liquid → Solid). • Pressure - 1) Solid: There is no effect of pressure on solids. 2) Liquid: There is no effect on pressure on liquid. 3) Gas: The volume of gas decreases with increase in pressure

13. SOLID – LIQIUD (Melting) On increasing the temperature of solids, the kinetic energy of the particles increases. Due to the increase in kinetic energy, the particles start vibrating with greater speed. The energy supplied by heat overcomes the forces of attraction between the particles. The particles leave their fixed positions and start moving more freely. A stage is reached when the Solid melts and is converted to a Liquid. The temperature at which a solid melts to become a liquid at the Atmospheric Pressure is called its Melting Point. The Melting Point of Ice is 273.16 K or 0º C. The process of change of solid state into liquid state is known as Fusion or Melting.

14. LIQUID – GAS (Boiling) When we supply heat energy to water, particles start moving faster. At a certain temperature, a point is reached when the particles have enough energy to break free from the forces of attraction of each other. At this temperature the liquid starts changing into gas. The temperature at which a liquid starts boiling at the Atmospheric Pressure is known as its Boiling Point. The Boling Point of water is 373 K or 100º C. Boiling is a Bulk Phenomenon. Particles from the bulk of the liquid gain enough energy to change into the vapor state. Therefore, the process of conversion of liquid state into gaseous state is known as Vaporization or Boiling.

15. GAS – LIQUID (Condensation) The phenomenon of change of gas to liquid is called Condensation. For instance, presence of Water Droplets on surface of glass containing cold water because the Water Vapor present in air comes in contact with the cold glass of water it loses its energy and condenses to liquid state.

16. LIQUID – SOLID (Freezing) The phenomenon of change of liquid to solid is called Solidification or Freezing. Freezing point is the temperature at which a liquid becomes a solid at normal atmospheric pressure.

17. SOLID – GAS (Sublimation) A change of state directly from solid to gas without changing into liquid state is called Sublimation. Substances that sublime are Ammonium Chloride, Camphor, Naphthalene Balls, Iodine and Dry Ice. • A change of state directly from gas to solid without changing into liquid state is called Deposition or ReverseSublimation.

18. INTERCONVERSION OF STATES OF MATTER

19. CONVERSION OF DRY ICE - Pressure can also be used to change the states of the matter. Applying pressure and reducing temperature can liquefy gases. • Conversion of Dry Ice – : Dry Ice is stored under high pressure. Solid CO2 gets converted directly to gaseous state on decrease of pressure to 1 Atmosphere without coming into liquid state. This is the reason that Solid Carbon Dioxide is also known as Dry Ice.

20. LATENT HEAT OF FUSION The word ‘Latent’ means Hidden. The amount of heat energy that is required to change 1 kg of a Solid into liquid at Atmospheric Pressure at its Melting Point is known as the Latent Heat Of Fusion. So, particles in water at 0º C (273 K) have more energy as compared to particles in ice at the same temperature because this heat gets used up in changing the state by overcoming Force of Attraction between the particles.

21. LATENT HEAT OF VAPORIZATION The amount of heat energy that is required to change 1 kg of a Liquid into Gas at Atmospheric Pressure at its Boiling Point is known as the Latent Heat Of Vaporization. So, particles in water at 100º C (373K) have more energy as compared to particles in ice at the same temperature because this heat gets used up in changing the state by overcoming Force of Attraction between the particles.

22. EVAPORATION The phenomenon of change of a liquid into vapors at any temperature below its Boiling Point is called Evaporation. • Factors Affecting Evaporation: - • An Increase in Surface Area • An Increase in Temperature • An Increase in Humidity • An Increase in Wind Speed

23. INCREASE IN SURFACE AREA Evaporation is a Surface Phenomenon. If the surface area is increased, the rate of evaporation increases. For example, while putting clothes for drying up we spread them out.

24. INCREASE IN TEMPERATURE With the increase of temperature, the water molecules move rapidly when the water is heated. This makes the molecules escape faster. Higher temperatures lead to increase in vaporization as more molecules get kinetic energy to convert into vapor.

25. INCREASE IN HUMIDITY Humidity is the amount of water vapor present in air. The air around us cannot hold more than a definite amount of water vapor at a given temperature. If the amount of water in air is already high, the rate of evaporation decreases.

26. INCREASE IN WIND SPEED With the increase in wind speed, the particles of water vapor move away with the wind, decreasing the amount of water vapor in the surrounding.

27. HOW EVAPORATION CAUSES COOLING ? • In an open Vessel – The liquid keeps on evaporating. The particles of liquid absorb energy from the surrounding to regain the energy lost during Evaporation. This absorption of energy from the surroundings make the surroundings cold. • When Acetone gets poured on Palm – The particles gain energy from your palm or surroundings and evaporate causing the palm to feel cool. • When some people pour water on the Rooftop on a Hot Sunny Day - People sprinkle water on the roof or open ground because the large Latent Heat of Vaporization of water helps to cool the hot surface.

28. WHY TO WEAR COTTON CLOTHES DURING SUMMERS? During Summer, we perspire more because of the Mechanism of Our Body which keeps us cool. In Evaporation, the particles at the surface of the liquid gain energy from the surroundings or body surface and change into vapor. The Heat Energy is absorbed from the body leaving the body cool. Cotton, being a Good Absorber of water helps in absorbing the sweat and exposing it to the atmosphere for easy evaporation.

29. PLASMA Thestate that is comprises of super energetic and exited particles is called Plasma. It is considered as 4th State of Matter. The Fluorescent Tubes and Neon Bulbs consist Plasma. Inside a Fluroscent Tube or a Neon Bulb the Gas gets Ionised, i.e. gets charged when electrical energy flows through it. This creates the Plasma glow inside. The Sun and the Stars glow because of the presence of Plasma in them. The Plasma inside the Stars gets created because of High Temperature.

30. BOSE – EINSTEIN CONDENSATE In 1920, Indian Physicist Satyendra Nath Bose had done some calculations based on 5th State of Matter. These calaculationswre revised by the great German Scientist, Albert Einstienand he predicted that there can be a new state of matter – Bose Einstein Condensate. In 2001, Eric A. Cornell, Wolfgang Ketterleand Carl E. Wiemanof USA received Nobel Prize in Physics for achieving “Bose – Einstein Condensate”. The BEC is formed by cooling a gas of extremely low density, to super low temperatures.

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