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Ch - 1 MATTER
IN OUR SURROUNDINGS
Class 9
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Syllabus – Matter - Nature
and Behaviors Definition of - Matter, solid, liquid, and gas. Characteristics shapes, volume, density. Change of state - melting (absorption of heat), freezing, evaporation (cooling by evaporation) condensation, sublimation. |
1. Matter - The matter is defined as one which occupies space,
has mass, and is realized by our sense.
Matters may be solid, liquid, or gas.
2. Latent heat - Latent heat is the hidden heat that is required to convert the matter from one state to another state without a change in temperature.
3. The latent heat of vaporization - The latent heat of vaporization is the quantity of heat in joules required to convert 1 kg of liquid to vapour or gas without a change in temperature.
4. The latent heat of fusion - The latent heat of fusion is the quantity of heat in joules required to convert 1 kg of solid to liquid without a change in temperature.
5. Sublimation - Sublimation is the process by which solid on heating directly changes into the gaseous state without a change in a liquid state and vice versa.
Example- Iodin, camphor, naphthalene, dry ice, etc.
change directly into a gaseous state when they are heated.
6. A sponge is solid while it is compressible like gas - A
sponge is solid and has many small holes, in which air is trapped. When we
press it, the air is expelled out and we are able to compress it.
7. The melting point of most of the substances increases with an increase in pressure. However, the melting point of ice decreases with an increase in pressure.
8. The necessity of heat energy to melt a solid - In a solid intermolecular force between the particles is very strong so heat energy is essential to overcome the intermolecular force.
9. Fusion - Solid-state on heating changes into a liquid state. This phenomenon is called fusion.
10. Diffusion - The rate of diffusion increases on heating because when the temperature of a substance is increased by heating, its particle gains kinetic energy and move more rapidly.
11. Diffusion helps aquatic animals and plants to survive in water- Diffusion is the property of gases that helps aquatic animals and plants to survive in water. Respiratory gases oxygen and carbon dioxide diffuse in water and helps them to breathe in the water.
12. Brownian motion. The rapid and zig-zag movement of tiny particles in a liquid is called Brownian motion. This motion increases on heating because the movement of tiny particles gain kinetic energy and move faster.
13. Two factors that determine the rate of diffusion
(a) Temperature - Diffusion increases with an increase in temperature.
(b) Density - Diffusion increases with a decrease in density.
14. The states of matter on the basis of kinetic theory -
(i) When the intermolecular forces between the particles
are strong, particles come closer and occupy a solid-state.
(ii) When the intermolecular force between the particles are weak, particles stay far apart from one another and occupy either liquid or gaseous state.
15. Liquefying of gas - When the pressure is increased on gas, the gas undergoes condensation that is it liquifies and changes into a liquid state.
16. Three states are interconvertible:
When the solid matter is heated, it changes into the liquid by absorbing
heat energy and this phenomenon are called melting.
17. The full form of LPG and CNG. -
Full form of LPG - Liquefied petroleum gas
Full form of CNG - Compressed natural gas.
18. Evaporation -When the liquid matter is heated, it changes into
the gaseous state by absorbing heat. This phenomenon is called
evaporation.
19. Condensation - Gaseous state on cooling changes into the liquid
state by releasing heat energy and this phenomenon are called condensation.
20. Atmospheric pressure - The pressure of air in the atmosphere is
called atmospheric pressure.
The atmospheric pressure at sea level is 760 mm of Hg or 76 cm of Hg.
1 atmosphere = 101325 Pa
21. The S.I units of
(i) Mass ----- Kg ( Kilogram)
(ii) Length ---- m
(iv) Temperature --- K ( Kelvin)
(v) Force -- N (Newton)
(vi) Volume --- m3( Cubic
meter)
(v) Density --- Kg/m3
(vi) Pressure -- Pa ( Pascal)
22. Dry ice - Solid carbon dioxide is called dry ice. It is used as
a cooling agent.
Carbon dioxide gas is first pressurized and cooled to form liquid CO2 and
once released to atmospheric pressure, the liquid carbon dioxide converts to
dry ice and CO2(g).
23. Frosting - Conversion of gas to solid directly without changing into a liquid is called frosting.
24. The smell of hot sizzling food reaches you several meters away, but to get the smell from cold food you have to go close. - The rate of evaporation, kinetic energy, and diffusion increases with the rise in temperature. Thus the smell of hot sizzling food reaches us from several meters away. The rate of evaporation, kinetic energy, and diffusion of cold food, comparatively less than hot food. So cold food realized only on coming closer.
25. A diver is able to cut through water in a swimming pool - A diver is able to cut through water in a swimming pool because of a weak intermolecular force of attraction between water molecules. The diver used streamlines action to reduce this force.
26. The characteristics of the particles of matter -
(i) Matter in either of the state (solid, liquid, or gas) is composed of very
small particles of molecules or atoms or ions.
(ii) The constituent particles, atoms, molecules, or ions
have space between them.
(iii) The particle of matter is held together by
intermolecular force.
(iv) Particles of matter are always in a state of motion.
(v) Particles of matter possess kinetic and potential energy.
27. The increase in temperature affect the rate of diffusion - Kinetic energy is possessed by particles of matter in motion. When the temperature is increased, kinetic energy increases, and the rate of movement of particles also increases. The higher the temperature, the higher the kinetic energy, and the faster the rate of diffusion.
28. The kinetic theory of matter - The theory which visualizes that any substance whether solid liquid or gas is made up of tiny particles atoms molecules or ions which are in constant motion is called the Kinetic theory of Matter.
29. We wear cotton clothes in summer - Because cotton cloths are a good absorber of water so in summer it absorbs sweat from our body and evaporates it in the atmosphere by absorbing the heat from our body and the heat of the body gets dissipated during evaporation of sweat and keeps us cool.
30. Differences between gas and vapour:
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Vapour i. A substance which under ordinary temperature is a
solid or liquid, but under specific conditions is gaseous, is called vapour. ii. It is a substance above its boiling point temperature. |
Gas i. Gas is a substance above its critical temperature but below its critical pressure. ii.It a substance that exists in the gaseous state under ordinary conditions.
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31. Differences between evaporation and boiling.
(a) Evaporation occurs at any temperature,
but boiling occurs only at boiling points.
(b) Evaporation produces a cooling effect,
but boiling produces a heating effect.
(c) It is a surface phenomenon, but boiling is a bulk phenomenon (whole part of the liquid).
32. What happens when the temperature of the solids increases - When the temperature of the solid is increased, the supplied heat absorbed by the constituent particles and therefore the kinetic energy of the constituent particles increases. Due to this and intermolecular the force of attraction decreases and inter-molecular space increases and solid starts changing into a liquid state.
33. On increasing the wind speed, the rate of evaporation increases - With the increase in wind speed, the particles of water vapour move away with the wind, decreasing the amount of water vapour in the surrounding. Hence evaporation increases.
34. Evaporation is a surface phenomenon - The particles of the surface of liquids which are in contact with surroundings, gain heat energy from surroundings and its kinetic energy increases, due to these particles of the surface of the water evaporate. So evaporation takes place at the surface of a liquid and we say that evaporation is a surface phenomenon.
35. A wooden chair should be called a solid and not a liquid - Because a wooden chair that is solid, have least and fixed inter-particle space between their molecules, constituent particles are closely packed and can vibrate about a fixed axis.
While in liquids they have more
inter-particle space between their molecules than solid, constituent
particles are loosely packed and free to move in such a way that they remain in
contact with one another. So a wooden chair is called a solid.
36. Evaporation causes cooling - Evaporation requires heat energy. The particles of surface liquid absorb this heat energy from its surroundings during evaporation and thus temperature is lowered and one feels cool.
37. Our palm feels cold when we put some acetone or petrol or petroleum on it - Due to evaporation of low boiling point liquids that is acetone by absorbing the heat from our palm.
38. The water kept in an earthen pot becomes cool during summer - In summer the temperature is more and evaporation becomes faster. The earthen pots are porous and allow the tiny water particles to get evaporated. The heat required for evaporation is supplied by water kept in the pot. So the water kept in an earthen pot becomes cool during summer.
39. A desert cooler cools better on a hot dry day - On a hot dry day, the temperature is more and humidity is low due to which the rate of evaporation of water becomes faster. Due to the increase in the rate of evaporation more water gets vaporized and cooling is better.
40. The interconversion of three states of the matter with the
the help of a chart.
(i) Solid to Liquid: Fusion
(ii) Liquid to Gas: Vaporization
(iii) Gas to liquid: Condensation
(iv) Liquid to Solid: Solidification
(v) Solid to Gas: Sublimation
(vi) Gas to Solid: Frosting
41. The various factors affect the rate of evaporation - Factors
affect the rate of evaporation:
I. Temperature- Evaporation increases with an
increase in temperature.
ii. Humidity - Evaporation
increases with a decrease in humidity.
iii. Wind speed- Evaporation increases with an increase in wind speed.
iv. Surface area-Evaporation increases with an increase in surface area.
42. Gases are more compressible - Force of attraction between molecules of gases is negligible due to which intermolecular space is maximum than solid and liquid. That is why gases are more compressible.
43. Reason of water droplets forming on the outer surface of a glass containing ice-cold water - The water vapour present in the atmosphere, on coming in contact with the cold glass of water and condense into water droplets (in liquid state).
44. During the summer, we perspire more - In summers temperature of the outside is more than our body temperature so to get equilibrium our body temperature starts increasing so as to cool our body sweat glands produce sweat so that it can evaporate and take the heat of our body hence cooling.
45. The level of water does not change when salt dissolves in water - When we dissolve salt in water, the level of water does not change because the particles of water are loosely packed and having space between them which is known as intermolecular space. This intermolecular space accommodates the salt particles.
46. Water boils below 100 degrees C at the mountain - Water boils when its vapour pressure becomes equal to the atmospheric pressure which is 76 cm of Hg. Atmospheric pressure at the mountain is less than 76 cm of Hg. So water boils below 100 degrees C at the mountain.
47. The heat energy is more in steam than in water at 100 degrees C or 373 K (100C + 273) - Particles in steam, that is, water vapour at 373 K (100 C) has more energy than water at the same temperature. This is because particles in steam have absorbed extra energy in the form of latent heat of vaporization.
48. The heat energy is more in the water at 0 degrees C or 273 as compared to particles in ice at the same temperature - particles in water at 0 C (273 K) have more energy as compared to particles in ice at the same temperature because particles in water have absorbed extra energy in the form of latent heat of fusion.
49. The differences in the characteristics of states of matter.
Solid | Liquid | Gas |
1. The constituent particles are tightly packed. | The constituent particles are loosely packed. | There is no definite arrangement in particles. |
2. The interparticle distance is fixed and is very small. | Inter-molecular space is small but greater than solid. | Intermolecular space is very large compared to the solid and liquid. |
3. Solid - Have definite shape, sizes, and volume. | Have no definite shape, and size but have a definite volume, it acquires the shape of containers. | Have no definite shape, definite volume, and size, it acquires the shape of containers. |
4. Solids are very less compressible. | Liquids are less compressible but more than solid. | Gases are highly compressible due to the presence of a very large space between the molecules. |
50. A gas fills completely the vessel in which it is kept - The particles of gas are free to move in any direction due to very weak the inter-particle force which is negligible, That is why a gas fills completely the vessel in which it is kept in
51. A gas exerts pressure on the walls of the container - Since the particles of a gas are free to move in all the possible direction, they strike the walls of the container with a definite force per unit area and exert a definite force under a given set of conditions to develop pressure.
52. A wooden table should be called a solid - In a wooden table, the constituent particles are unable
to exert translational motion because they are held together by strong cohesive
forces due to which wood has definite shape, volume, and size. Therefor a
wooden table is called a solid.
53. We can easily move our hand in the air but to do the same through a solid
block of wood we need a karate expert - The constituent particles of
wood which is solid held together by strong intermolecular force, the movement
of hand through a solid block of wood, therefore, require a large amount of
energy to separate the particles so only a karate expert is able to exert such
a large force and is able to do so.
54. While putting clothes for drying up we spread them out - Spreading the cloths for drying increases the surface area which helps it to dry faster as the rate of evaporation increases with an increase in area.
55. Clothes dry up faster when spread near a heater - Clothes dry up faster when spread near a heater because the heater increases the temperature which helps it to dry faster as the rate of evaporation increases with an increase in temperature.
56. Clothes take a very long time to dry on a rainy day - Clothes take a very long time to dry on a rainy day
because the rate of evaporation decreases with an increase in humidity.
57. Reason after a hot the sunny day people sprinkle water on the roof or open ground - After a hot sunny day roof and the open ground become hot. When people sprinkle water, it evaporates and leads to a decrease in temperature because water takes heat from the floor and ground for evaporation.
58. The smell of lighted incense stick reaches you several meters away, but to get the smell from until incense stick you have to go close - The rate of evaporation, kinetic energy, and diffusion increases with the rise in temperature. Thus the smell of lighted incense stick reaches us from several meters away.
The rate of evaporation, kinetic energy, and
diffusion of until incense stick, comparatively less than lighted incense
stick. So until incense stick realized only on coming closer.
59. The naphthalene balls disappear with time without leaving any solid - Naphthalene balls are the sublime substances, so the naphthalene balls disappear with time without leaving any solid, in which substances are directly changed into the gaseous state without a change in liquid.
60. The rate of diffusion is faster in gas -
i. Force of attraction between molecules of
gases is negligible due to which particles can move freely.
ii. The kinetic energy of particles of gas is
more than solids and liquids.
That is why the rate of diffusion is faster
in gas.
61. Gases exert pressure on the walls of containers - Force of attraction between molecules of gases is negligible due to which particles of gases can move randomly in all directions. During the motion, they collide with each other and also with the walls of the container.
62. The rate of diffusion
of liquids is higher than that of solids - In the liquid state, the force of attraction
between the constituent particles is less than solid, particles move freely and
have greater space between each other as compared to particles in the
solid-state. So the rate of diffusion of liquids is higher than that of
solids.
63. Bose-Einstein Condensate - The BEC is formed by cooling a gas
of extremely low density, about one-hundred-thousandth the density of normal
air, to super-low temperatures. It was predicted by Albert Einstein in
2001, Eric A.
64. Plasma state of matter - The plasma is the fourth state of
matter consists of super energetic and super excited particles in the form of
ionized gases. In the fluorescent tube and neon sign bulbs neon gas and helium
gas or some other gases get ionized when electrical energy flows through it.
This ionized gas creates a plasma glowing inside the tube or bulb. The plasma
glows with a special colour and depends on the nature of the gas. The Sun and
the stars glow due to the presence of plasma in them. The plasma is
created in stars due to very high temperatures.
65. The interconversion of the state of matter is considered as a physical
change - The interconversion of the state of matter is considered as a
physical change as:
i. there is no change in the chemical properties of the matter.
ii. no new substance is formed, the substance remains the same in the different states.
iii. it is a reversible change, a substance
can back to its original state by physical means.
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