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UNIT-1 Matter in our surroundings - BBPS-Mumbai...2020/04/09 · Matter in our surroundings PART-4...
Transcript of UNIT-1 Matter in our surroundings - BBPS-Mumbai...2020/04/09 · Matter in our surroundings PART-4...
UNIT-1Matter in our surroundings
PART-4 EVAPORATION AND BOILING
PREPARED BY – MEENAKSHI TIWARI
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Evaporation
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•Particles of matter are never at rest
•Particles of matter possess kinetic
energy
The particles of liquids have more kinetic
energy easily overcome the forces of
attraction and convert into vapor without
any external forces.
The phenomenon of change of a liquid into
vapors at any given temperature below its
boiling point is called Evaporation.
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Factors Affecting Evaporation
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Condition Rate of Evaporation Reason
Increase in Surface Area IncreasesParticles have more space and thus
can evaporate easily
Increase in temperature IncreasesKinetic energy among the particles
increases
Increase in humidity DecreasesWater content in air increases and so
evaporation decreases
Increase in wind speed IncreasesWater vapours are blown away by
winds allowing more evaporation
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How evaporation causes cooling?
The process of evaporation uses the energy of the liquid
particles.
Therefore, the particles absorb energy from the
surroundings in order to compensate the energy that is
being lost in the process of evaporation.
This results in cooling of the surrounding area.
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Examples of EvaporationOur palms feel cool when we put some acetone (nail
paint remover) on it.
People sprinkle water on their roofs or ground on sunny
days to cool the area.
We are able to sip hot tea faster in a saucer than in a cup
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Try Answering Following
Why people wear cotton clothes in summer?
Why water droplets appear on the
surroundings of a glass with ice-cold water?
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SI Unit of Mass Kg (Kilogram)
SI unit of Volume m3 (cubic meters)
Common unit of Volume L (Liters)
SI unit of temperature
Kelvin
0O C = 273.16 K or 273 K (approximately)
Kelvin = Celsius + 273
Si unit of Pressure Pa (Pascal)
For measuring pressure exerted by Gas
Atmosphere (atm)
1 atm = 1.01 X 105 Pa
Normal Atmospheric Pressure = 1 atm (at sea level)
Important Measurement Units
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https://youtu.be/jhTSRojj8K8
https://www.learncbse.in/matter-surroundings-cbse-
notes-class-9-science/
WORKSHEET-3
INTERCONVERSION OF STATE
BBPS NM
1. Why does a desert cooler cool better on a hot dry day?
2. How does the water kept in an earthen pot (matka) become
cool during summer?
3. Why does our palm feel cold when we put some acetone or
petrol or perfume on it?
4. Why are we able to sip hot tea or milk faster from a saucer
rather than a cup? 5. What type of clothes should we wear
in summer?