class 9th chapter 1st chemistry notes
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Answer:
Matter:
Anything that occupies space and has mass is called matter.
It exists in the form of five basic elements, the Panch tatva – air, earth, fire , sky and water.
For example: Chair, bed, river, mountain, dog, tree, building, etc.
Characteristics of matter:
Matter is made up of small particles called atoms.
These particles are too small to be observed with naked eye.
These particles are constantly moving constantly.
These particles have spaces between them.
Particles of matter attract each other because of the force of attraction.
Diffusion:
Particles of matter intermix on their own with each other. They do so by getting into the spaces between the particles. This intermixing of particles of two different types of matter on their own is called diffusion.
Applications of Diffusion:
Dissolving a solid in a liquid:
When a crystal of potassium permanganate is placed in a beaker of water, the water slowly turns purple on its own, even without stirring.
Both potassium permanganate crystal and water are made up of tiny particles.
When the potassium permanganate crystal is put in water, the purple colored particles of potassium permanganate spread throughout water making the whole water look purple.
Actually, on dissolving, the particles of potassium permanganate get into the spaces between the particles of water.
This shows that the particles have spaces between them and are continuously moving on their own.
Mixing of two gases:
Fragrance of an incense stick (agarbatti) lightened in one corner of a room, spreads in the whole room quickly.
The particles of gases (or vapours) produced by burning the incense stick move rapidly in all directions and mix with the moving particles of air in the room
This also shows that the partices of matter are constantly moving.
Brownian motion of particles (By Robert Brown):
The random or zig-zag movement of microscopic particles in a fluid, as a result of continuous bombardment from molecules of the surrounding medium, is known as Brownian motion.
For example: Dust moves randomly because the random moving particles of air collide with dust particles.
Basis of Classification of Matter:
Based upon particle arrangement
Based upon energy of particles
Based upon distance between particles
Three States of Matter:
Solid
Liquid
Gas
Constituent particles are very closely packed.
Constituent particles are less closely packed.
Constituent particles are far apart from each other.
Force of attraction between particles is very strong.
Force of attraction between particles is less strong.
Force of attraction between particles is negligible.
Force of attraction between particles is very strong.
Kinetic energy between particles is more than that in solids.
Particles have maximum kinetic energy.
Have definite shape and volume.
Do not have definite shape but definite volume.
Neither have definite shape nor definite volume.
Have high density and and can not be diffused.
Density is lower than solids and can diffuse.
Density is least and can easily diffuse.
Incompressible.
Almost incompressible.
Highly compressible.
On increasing the temperature of solids, the kinetic energy of the particles increases which overcomes the forces of attraction between the particles thereby solid gets converted to a liquid.
Melting: Change of solid state of a substance into liquid is called melting.
Melting point: The temperature at which a solid melts to become a liquid at the atmospheric pressure is called its melting point.
Melting point of ice is 0oc.
(a) Liquid to gas:
On heating a liquid like water, the kinetic energy of its particles increases as high as in a gas, thus causing the liquid to change to a gas.
Boiling: The change of a liquid substance into gas on heating is called boiling.
Boiling point: The temperature at which a liquid boils and changes rapidly into a gas at the atmospheric pressure is called its boiling point.
Boiling point if water is 100oC.
(b) Gas to liquid:
On cooling a gas like steam (or water vapour), the kinetic energy of its particles is lowered down, causing them to move slowly and bringing them closer, forming a liquid.
Condensation: The process, in which a gas, on cooling, turns into a liquid at a specific temperature is called condensation or liquefaction.
(c) Liquid to solid:
When a liquid is cooled down by lowering its temperature, its particles lose the kinetic energy and come to a stationary position, causing the liquid to turn to soilid.
Freezing: The change of a liquid substance into soilid by lowering its temperature is called freezing.
Freezing point: The temperature at which the state of a substance changes from a liquid to a solid is called the freezing point of that substance.
Fusion:The process of melting, that is, change of solid state into liquid state is also known as fusion.
Latent heat: The heat energy that is required to change the state of a substance without causing any ruse in the temperature of the substance is called latent heat. Since, the heat energy is hidden in the bulk of the matter, it is called latent heat.
Explanation:
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