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Chapter 15: Online NCERT Summary Class - VI (Science) for UPSC CSE
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This lesson deals completely with the concepts of Chapter 15 Air Around Us, from class 6 Science NCERT. We are surrounded from Air everywhere and the thin layer which surrounds earth is known as atmosphere. These kinds of basic information about Air is completely discussed in this lesson. Then using a chart he elucidates the amount of gases like Nitrogen, Oxygen, Argon. Carbon-di-oxide, Neon, helium, and Methane, available in the dry air. The has also listed the layers of Atmosphere and the distance of them in between. Then he takes Troposphere​, Stratosphere, Mesosphere, Thermosphere and Exosphere and gives their brief one by one.

Roman Saini is teaching live on Unacademy Plus

Roman Saini
Part of a great founding team at Unacademy with Gaurav, Hemesh. Movies, Guitar, Books, Teaching.

Unacademy user
This summary course is very helpful sir.I use to take time while making notes but through this I have completed 6 class ncert in one day only.Thank you very much sir.please make such course for 7-12 class ncerts also.
Thank you so much sir! Please make courses on class 7 and 8 ncert science as well!
sir please make summary for 7th to 10th ncert science. please sir
Happy a lot... at last I completed 6th NCERT science :) :) Thank you Roman sir.
sir pls make course for class 7th to 10th it wil be grt hlp for us . tyu in advance
  1. Class 6 Science NCERT Part 9: Chapter 15 Presented by Dr. Roman Saini

  2. About me MBBS, AIIMS 706-1334 EST Cleared CSE-2013 Loves playing Guitar, Movie Buff * Course Fee : Contribute Follow me on Unacademy

  3. Chapter 15: Air around us Air is everywhere, in water, soil, surroundings (except vacuum), moving air is wind Air occupy space (empty bottle pushed in water, feel the resistance), has no color, is transparent * Thin layer of air surrounding earth: Atmosphere why do mountaineers carry oxygen cylinders with them, while climbing high mountains * Air: Mixture of water vapour, Oxygen (water rise, inverted glass, candle burns), Nitrogen, CO2, Dust and smoke (prevented by fine hair and mucus in our nostrils)

  4. Take 2 glass, one bigger than other, invert them over a burning candle, in a tumbler with some water (mark the water level) Candle will stop burning first in the smaller glass, as oxygen is less in that. Space occupied by oxygen is filled by water and the water level rises. Still the space in the glass remains as large majority of air is made up of Nitrogen. Mucus, fine hair present inside nose prevent dust particles from entering RS

  5. % in dry air (atmosphere) 78.08% 20.95% Gas Nitrogen Oxygen Argon CO2 0.93 0.0397 0.04 0.001 0.0005 Neon Helium Methane 0.0001 Water vapour = 0.001 5 %, strong local variation, 0.25% overall earth, not included in above calculation air is dry)

  6. Atmospheric layers . Troposphere (0-12 kms.9 @ poles, 17 @ equator) Stratosphere (12-50 kms) o Mesosphere (50-80 kms) Thermosphere (80-700 kms) s Exosphere (700-10,000 kms)

  7. s- turn): Extends from Earth's surface till Tropopause, followed mostly by temperature inversion i.e. warm after cold or by a isothermal zone Temp falls with increasing altitude (rule of thumb), heating occurs from surface and above 80% of atmospheric mass (50% in just lower half) propeller based) s Almost all water vapour, moisture, weather, clouds, aircrafts (especially

  8. Stratosphere: Tropopause to stratopause, Ozone O3 , Temp rises with altitude because of absorption of UV rays by ozonosphere Free of air turbulence * Highest layer for aircrafts (jet-powered) Polar stratospheric or nacreous clouds forms above tropopause

  9. Mesosphere: Stratopause to mesopause * Coldest place on earth (-850C average) * Temp falls as altitude rises, just like troposphere Water vapour sublimes and form noctilucent clouds, highest clouds in atmosphere Most meteors burn here Too high for aircrafts, too low for satellites Accessible by sounding rockets

  10. Thermosphere:MesopausetoThermopauseorExobase, Lower half have ionosphere, temperature rises upto 1500 C, due to extreme rarefaction i.e. density of molecules is very low, not meaningful temperature PV-NKBT, If skin comes in contact with thermosphere, the pressure is so low that not much transfer of energy will happen and you will not feel hot, despite high temperature. Absolutely free of water vapours hence cloudless International space station (320-380 kms) Aurora borealis and australis occurs (natural lights seen in higher altitude, due to ionisation, interaction of T/E with magnetospheric plasma, cosmic rays, solar wind

  11. Noctiluscent cloud 80 km K rm n line 100 km Aurora Mesopause 80 km Mesosphere Stratosphere Troposphere i Stratopause 50 km Ozone layer Tropopause 12 km Meteors Nacreous cloud 15-25 km Cumulonimbus clouds Cirrus clouds 6-12 km Weather balloon 40 km Contrails 6-12 km

  12. , Air helps in : Photosynthesis: Takes CO2 in and produce O2 Respiration: Takes 02 in and produce CO2 Windmill: Draw water from tube-wells, generate electricity, run flour mills, mechanical jobs Movement of sailing yachts, gliders, parachutes, aeroplanes, birds can fly Pollinating agent, dispersal of seeds and water cycle

  13. Put water in soil, you will see bubbles coming out Burrows and holes helps in enriching soil and underground dwelling space, with air Plants are net producer and hence replenisher of oxygen in the atmosphere Inter-dependence for exchange between plants and animals for oxygen and carbon dioxide

  14. Why earthworm comes out of soil in heavy rains? Ans. Water displaces dissolved oxygen

  15. How will you show that air is dissolved in water? Ans. Boiling

  16. Why does a lump of cotton wool shrink in water? Ans. Air is replaced by water Why dote lns Air is replaced by water