Class 6 Science NCERT Summary By Dr. Roman Saini

Chapter classification - Biology

● Food- Where does it come from

● Components of food

● Getting to know plants

● The living organism and their surrounding

● Body movements

Chapter classification - Physics

● Motion and Measurement of Distances

● Light, Shadows and Reflections

● Electricity and Circuits

● Fun with Magnets

Chapter classification - Chemistry

● Fibre to Fabric

● Water

● Air around us

● Garbage in, garbage out

● Sorting materials into group

● Separation of substances

● Changes around us

Ch 1 and 2: Food: Sources and components

● Food variety: ingredients, edible, sources (plants and animals), dry seeds, sprouts, nectar, herbivores, carnivores, omnivores

● Nutrients: carbohydrates (starch+sugars), proteins, fats, vitamins and minerals, food also have dietary fibres and water

● Starch + iodine = blue black

● Proteins + CuSO4 + Caustic Soda (NaOH) = violet

● Fat + Paper crushing of food = oily patch + light passing (translucent)

● Carbs = energy, fat = much more energy, proteins = body building material

● Vitamins: proper growth of body and to maintain good health. Ex: A, B complex, C, D, E, K

● Vitamin A keeps our skin and eyes healthy. Vitamin C helps body to fight against many diseases. Vitamin D helps our body to use calcium for bones and teeth

● Dietary fibres: Roughage, plants (whole grains, pulses, vegetables, fresh fruits), no nutrition, provide bulk, get rid of undigested food and is an essential component

● Water: absorbs nutrients excreting wastes from body (urine and sweat).

● Sources: Water, milk and tea, food, metabolic by product.

● Balance diet: Combination of food, all nutrients+roughage+water, body needs, in right quantity, neither too little nor too much, growth, maintenance, good health

● Don’t peel, don’t wash too much, don’t overcook (Vitamin C gets destroyed), nutrition may be lost

● Not too much fat in diet, otherwise it will lead to obesity

● Lack of a particular nutrient in the food causes deficiency diseases.

Ex: lack of protein over a period of time: stunted growth, swelling of face, discolouration of hair, skin diseases and diarrhoea

● Prevention of deficiency diseases: take a balanced diet

Vitamin Deficiency disorder Symptoms Source

A Loss of vision Poor vision, loss of vision in darkness

(night)

Pulses (Soyabean, grams), Dairy (Milk, paneer)

eggs, meat

B1 Beriberi Weak muscles and very little energy to work Liver

C Scurvy Bleeding gums,

wounds take longer time to heal

Guava, lemon, orange, amla

D Rickets Bones become soft and bent

Milk, butter, egg, fish oil

Nutrient Deficiency disorder Symptoms Source

Ca Bone and tooth decay

Weak bones, tooth decay Milk and dairy

I Goiter

Glands in the neck appear swollen, mental disability

in children

Sea weeds, algae, sea food (veggie) organic yoghurt,

cranberries

Fe Anaemia Weakness Egg, liver, red meat, dried beans

Ch 3: Fibre to fabric● Fibres: cotton, wool, silk or synthetic. Cotton, wool (rabbit, yalk, camel,

sheep, goat), silk (cocoon), jute: Natural fibres; Polyesters nylons: synthetic

● Loose thread - yarn- can be pulled. Thin strands in a single yarn- fibres. Spinning (making yarns from fibres using takli or charkha)

● Yarns into fabric - weaving (looms) and knitting

● Cotton bolls, burst, seeds with cotton fibres (machine or hand separation is called ginning of cotton bolls)

● Jute: Stem, West Bengal, Bihar, Assam, Bangladesh, stem immersed in water for few days, rotting of stem, fibres are separated

● Clothing in ancient times: Leaves, twigs, Vines, animal fleece or hair were twisted together into long strands

● Flax in nile

FabricFibres Yarns

Spinning Weaving

Knitting

Ch 4: Sorting material into groups

● 1 Object = 1 or many materials

● 1 material = many objects

● Grouping helps in systematic arrangement and better study, analysis etc.

● Metals like aluminium, iron, copper have lustre (gentle sheen or soft glow), action of air and water = lose it (rust etc.)

● Hard or soft - Mohs scale of mineral hardness (1 to 10 - talc to diamond, scratch)

● (1) talc; (2) gypsum; (3) calcite; (4) fluorite; (5) apatite; (6) orthoclase; (7) quartz; (8) topaz; and (9) corundum (10) Diamond

● Soluble or insoluble; Transparent or translucent

Ch 5: Separation of substances● Make it fitter, purer for use; handpicking for slightly larger impurities;

separate grain from stalks etc. - threshing; using wind for separation - winnowing (heavy grain particles falls, lighter particles are blown away), sieving; passing of smaller particles though minute holes while retention of larger particles

● Sedimentation: When the heavier component in a mixture settles (followed by water addition), Decantation: Removal of water and impurities, Filtration: Passing though strainer, filter should have pores smaller than impurities.

● Evaporation: Water into vapour, happens at all the temperatures continuously, wherever water is present

● Process of conversion of vapour into its liquid form is called condensation.

● When no more solute can dissolve in a solution, it is saturated (saturation point varies from solute to solute and solution to solution)

● More solute can be added in a solution, if its temperature is increased.

● If temperature is decreased (cooling) the solute precipitates out.

● Lemonade is prepared by mixing lemon juice and sugar in water. You wish to add ice to cool it. Should you add ice to the lemonade before or after dissolving sugar? In which case would it be possible to dissolve more sugar?

Ch 6: Changes around us

● Reversible and irreversible

● Heat makes matter expand, cooling contracts

● Physical changes can be reversed using physical means only (exception alloys, evaporation, condensation, sublimation, desublimation or deposition)

● Chemical changes are usually not reversible using physical means alone (they need a chemical reaction to be reversed, ex: hardening of cement, POP, rusting of iron etc.)

Ch 7: Getting to know plants

● Stem, branches, roots, leaves, flowers of the plant

● herbs (green, tender stems, without many branches) , shrubs (hard stem, branching out near the base) and trees, creepers (spread on ground), climbers (take support and rise high)

● Stem conducts water, minerals, nutrients

● Leaf: petiole (part attaching to branch), lamina (broad green), midrib (thick vein), leaf venation (lines from midrib- reticulate in dicots ex: magnolia, ficus, China-rose, coriander; parallel in monocots, grass, banana, wheat, maize)

Ch 7: Getting to know plants

● Transpiration: water coming out from leaves through evaporation.

● Photosynthesis: food making using chlorophyll, water, CO2. Oxygen and starch are given out.

● Roots: absorption, anchoring, holding, tap and lateral roots, fibrous roots.

● When majority of plant food is stored in roots, they become edible. Ex: carrot, radish, sweet potato, turnip and tapioca

● Parts of a flower: Petals, sepals, stamens and pistils

● Petals (prominent), sepals (shy, buds, leaf like)

● Stamens (male: anther and filament) and pistil (female, innermost: stigma, style, ovary containing ovules)

● Tap roots = reticulate venation, Fibrous roots = parallel venation

● Herbarium: Collection of leaves in a book

Ch 8: Body movements

● Run, fly, jump, creep, crawl, slither, swim, walk

● Joints: Articulation between bones, cartilage, tendons etc. Movement (except at skull, sacral, sternal, and pelvic bones) and stability

● Ball and socket joint- cavity (hollow space) + head/ball of a bone, huge range, shoulder and hip joint

● Pivotal joint- Neck (median atlanto-axial joint), Radio ulnar joints (both), only rotation allowed

● Hinge joint: movement only on one axis- wrist and knee joint

● Fixed joint: Cant move, skull joints, upper jaw with skull

● Skeleton - framework of bones in our body, gives us shape, can be seen in an X-Ray.

● Rib cage:

○ Sternum (chest bone) + Vertebral column are connected thorough 24 (12*2) ribs, 7 (true ribs, attach directly to sternum) + 3 (false ribs, attach through coastal cartilages to 7th rib + 2 (floating ribs, hanging ribs) - called thorax, thoracic cavity

● Shoulder bones - bones on the back, Pelvic - bones below the stomach

● Skull - encloses the brain

● Some parts of the skeleton are not as hard as the bones and can be bent. These are called cartilage.

● 206 bones

○ 126 : Appendicular = 30*4 limbs - 120, 2 clavicles, 2 scapulas, 2 Pelvic bones, 120 + 6 = 126

○ 80 : Axial = Skull (29 - 22 Cranium + 6 ears + 1 hyoid), Vertebral column (7 C, 12 T, 5 L, 1 S, 1 C = 26), 24 Ribs + 1 Sternum.

○ 29 Skull + 26 Vertebral Column + 24 Ribs + 1 Sternum = 80

206 bones

● 126 : Appendicular = 30*4 limbs - 120, 2 clavicles, 2 scapulas, 2 Pelvic bones

● 80 : Axial = Skull (29 - 22 Cranium + 6 ears + 1 hyoid), Vertebral column (7 C, 12 T, 5 L, 5 S, 1 C = 32), 24 Ribs + 1 Sternum

● Muscles: contraction to bulging (shorter, stiffer and thicker), works in pairs (contraction + relaxation), only pull, at least 2 muscles are required to work for movement on a joint.

● Earthworm has muscles, no bones, tiny bristle hairs, eats soils and moves forward and excrete, very helpful for farming.

● Snails have one shell, which is dragged by strong foot muscles.

● Cockroaches have 3 pair of legs, can walk, climb and fly, thick exoskeleton with joints.

● Birds have pneumatic and hollow bones with strong muscles.

● Fishes have small head and tail, with streamlined body, series of jerks in strong muscles, with tail assisting in the direction, fins help in the balance.

● Snakes slither, forming loops (give forward push by pressing against the ground, sideways and not in a straight-line), long backbone, small muscles, interconnecting backbone, ribs and skin.

Chapter 9: Living organisms and their surroundings● Organisms live in a habitat and are adapted to it. Ex: Saline, desert, ocean,

normal land, forests

● Adaptation: Specific features or practices which improves the probability of survival of an organisms in his surrounding. 100s to 1000s of years

● Desert:

○ Camels: long legs keep it away from sand heat, no sweat, highly concentrated urine, dry dung; snakes etc.- deep burrows.

○ Cactus: leaves modified into spines (reduce transpiration losses), thick waxy fleshy green stem for photosynthesis, deep roots.

● Ocean: Streamlining, gills, oil, slippery fins, flat fins and tails, In sea, they use dissolved oxygen, squids and octopus make themselves streamline while moving.

● Dolphins and whales: no gills as they are mammals (nostrils or blowholes on upper part of their head). They go near surface to breathe from time to time, else they will die.

● Lakes: Roots are just to hold it in place, stems are long, hollow and light, grows till the surface, leaves and flowers float on the surface of water.

● Totally submerged plants: Narrow and thin, ribbon like leaves or highly divided leaves, so that strong current can just pass through them.

● Frogs: strong legs, webbed feet.

● Seed sprouting: germination● Habitat: Surroundings where organisms live - terrestrial and aquatic; biotic

and abiotic component (air, light, temperature, soil).● High mountains: Cold, windy, snowfall.● Tree: cone shaped, needle like leaves, sloping branches (rainwater and snow

slides, rather than staying)● Animals: thick skin, fur with long hairs, strong hooves (mountain goats,

climbing on rocks)● Grasslands: Predators like lion - light brown color, camouflage, withdrawing

of claws in toes, eyes placed in front (better estimate of prey’s location) ● Prey like deer: fast and light, strong teeth for chewing on stems, eyes placed

on side, long ears to hear the movement.

Criteria of being alive● Food/ source of energy● Growth● Respiration (not breathing) : Physiological and cellular respiration

○ Earthworm- skin, Fish - gills (dissolved oxygen in water), plants - stomata helps in exchange of gases (night time usually), oxygen consumed during respiration is much less than oxygen release during photosynthesis

● Response to environmental change (stimulus) - reflexes and conscious response, Mimosa pudica (touch-me-not), sunflower responds to sunlight○ Animals run away on flashing light, Cockroach hide if light is flashed

● Excretion: Removal of waste products, preset in food and otherwise generated in metabolic reactions. Ex: Sweat, feces, urine, skin secretions, respiration.

○ Plants either secrete out in the form of resins, latex, gum or store in secluded parts.

● Reproduction: procreation + biological process leading to new individual organisms (offspring) + produced from parents. Ex: Eggs, seeds, cuttings, live births

● Movement: from one place to other, or in plants: over and under the ground, with intra-organismic transfer of water, nutrients, food, minerals etc.

● Virus: organisms at the edge of life.

● Euglena: Both plant (autotroph) and animal (heterotroph) like features.

● Archaea: Neither bacteria nor eukaryotes. Extremophiles. Ex: methanogens.

● Sulfur bacteria: Oxidise sulfur (oxygen will kill them instantly).

Summary: Living beings need food, respire, respond to stimuli, reproduce, show movement, grow and die.

Chapter 10: Motions and measurement of distances ● Boats: simple log of wood with cavity, modified to resemble shape of aquatic

animals (streamline)● Till early 19th century, animal power (burden beast). Steam engine invented

in 18th C by Newcommen, improved upon by Watts, but it got popular only in the 19th century.

● 19th century = Railways became commonplace (India is one of the first countries in the world).

● 1910s = Aeroplane - commercial and army● 20th century: Electric trains, monorail, supersonic aeroplanes, spacecraft,

satellite

● Distance vs displacement

● Measurements of length is extremely important and need of gold standard is essential

● Unit : Fixed basic unit of measurement (Standard unit of measurement)

● Result of measurement : Unit + number

● 1790: French a standard called metric system (SI units)

SI base unit Physical Quantitymetre length

kilogram masssecond timeampere electric currentkelvin temperature

candela luminous intensitymole the amount of substance

● Metric prefix or SI prefix

○ yotta, zetta, exa, peta, tera

○ giga, mega, kilo, hecto, deca

○ deci, centi, micro, mili, nano

○ pico, femto, atto, zepto, yocto

Storage device CapacityFloppy KBs

CDs/ Pen Drives MrsDVDs / Pen

Drives GBs

Hard disks TBsServers PBs

● Straight line/ Rectilinear motion: Between 2 points

● Circular/Rotational motion: distance from a fixed point remains the same. Ex: Fan

● Periodic motion: Pendulum. Repeats itself after sometime

● Rolling motion: Rectilinear + Rotational. Ex: ball

Chapter 11: Light, shadows and reflections● Luminous objects: objects emitting their own light. Ex: Stars like sun

● Light will fall on an object first and then it will travel to our eyes, only then it will be visible (unless it is luminescent)

● On the basis of visibility, passage of light, objects are: Transparent (absolutely clearly), opaque (nothing at all) and translucent (not very clearly, somewhat in middle).

● Shadow: opaque, light, reasonably close screen in the background, gives an idea about shape of object, may mislead also.

● Light travels in a straight line.

● Pinhole camera: A light proof box, without a lens, with a single small aperture (pinhole). Light passes through this single point and produces an inverted image on opposite wall of the box.

● Natural pinhole: Small spaces in between tree leaves.

● Reflection: Change in direction of light (technically wave front) between 2 different media and its return in media of origin.

● Mirrors, lakes, ponds etc. are reflecting surfaces.

● Periscope: Instrument which makes observation of an object possible, which is otherwise not in direct line of sight of observer’s current position.

Chapter 12: Electricity and Circuits

● Electricity: Physical phenomenon - presence and flow of electric charge. Leads to lightning, static electricity, electromagnetic induction and electrical current.

● Carelessness : Can cause injury, including death (Our body is a conductor)

● Electric cell: Metal cap (+) metal disc (-), chemicals stores electricity, once started it goes on depleting (even when not in use). Alessandro Volta

● Joining these 2 ends without a switch or device, leads to consumption of chemicals very fast.

● Electric bulb: Thin wire in bulb that gives light - filament (W, Tungsten, break leads to bulb being fused). Bulb also has 2 terminals (base + metal tip of base, fix so they don't touch each other). Thomas Alva Edison

● Filament of the bulb is connected to its 2 terminus. Bulb glows when electric current passes through it.

● Material that allows current to pass through them : Conductor (metals like copper, silver, iron), Switches, electrical plugs and sockets

● Doesn’t allow current, high resistivity: Insulator (air, plastic, rubber, wood, ceramic, polyethylene, paper, mineral oil), touchable or exposed parts are covered by insulators- electrical wires, plug tops, switches

● Switch: simple device used to break/complete electric circuit.

● Closed electric circuit: Electric current passes from one terminal to another, direction of current is form + terminal to - terminal

● Why rubber gloves are used by electricians, screwdrivers, testers also have plastic covering: (rubber is bad conductor).

Chapter 13: Fun with magnets

● Magnet: any object which produces a magnetic field, attracting iron; Crane picking up heap of iron junk, cars.

● Magnes, Magnesia, Magnetite (Natural magnetic ores of Iron)

● Magnetic field- Invisible

● Materials not attracted to the magnet are non-magnetic.

● Interaction: Ferro, Para, dia, Ferri, Anti-ferro

● Magnetic: Those objects which get attracted to magnets. Ex- Ferromagnetic substances: Fe, Co, Ni, Lodestone, few alloys of rare earth metals, magnet

● Shape: bar magnet, horse-shoe magnet, cylindrical or a ball- ended magnet.

● Artificial magnets: Process of making magnets from iron.

● Poles: Most objects are attracted towards end of bar magnet.

● Direction: Freely suspended bar magnet- rest in North-South direction only, sun (E or W) or north star can also be used for determining direction

● Poles: North (N seeking end) and South (S seeking end) (Every magnet have them, regardless of shape)

Compass: Take a needle, find out its north pole, paint it

● Magnetised needle (free rotation) in a small glass box, dial with direction marked on it

● Place it where you want to know the direction

● Rotate till N and S on dial comes exact opposite to each other

● You now have the direction

● Travellers, sailors: suspended magnet from a thread, compass

● You can make a temporary magnet by moving a bar magnet with slight contact, along the length iron bar, to and fro (in particular direction, and with a particular pole)

● Attraction: Different poles; Repulsion: Same poles

● Physical pressure: Loss of magnetism, increase in temperature, hammering, trauma, drop from height, not stored properly

● Store in pairs such that unlike poles on same side, separate by wood, 2 soft iron pieces needs be placed across their ends. Horse shoe magnet: Soft Iron across their ends.

● Keep away from TV, Computers, mobiles, CDs, music system.

● A compass can be used to find East-West direction at any place.

● How will you know which pole is North or South?

A freely suspended magnet always aligns in N-S direction.

Chapter 14: H2O

● 89% - Safe drinking water, 750 million i.e. 1/9 no safe water to drink

● 71% of earth surface is covered by water.

● 40-90% (average 70%) water which human uses goes to agriculture.

● Average global water footprint of an individual is 1,385 m3 per year

● 5-10 K L : Average water consumption daily

● India- 1100 m3; USA- 2900 m3

● Water use: Toilet flush, power/energy, showers/bath.

● More mobile phone > Toilet, not only in India but entire world.

● 4 billion taps, 2.3 billion well/public sources (problem of washing, leaks, unpotable)

● Every minute = One child dies due to a water related disease

● 130- 150 millions hours each day = Time spent in collection of water

● Four times economic returns on spending on water and sanitation, if you spend 10$, you will get 40$ in return

● 97.5% Saline having 3.5% or 35 parts per thousand salts (96.5% Oceans, 0.9% other saline), 2.5% Freshwater (not much salts, <0.35 parts per 1000 or <1% of ocean salinity or < 0.035%)

● Out of this 2.5%, 68.7% Glaciers/Ice caps + 30.1% Groundwater = 98.8%; Rest is 1.2% (0.3% surface water, 0.9% other water).

● Of this total 1.2%, 69% is Ground ice/ permafrost, 20.9% lakes, 3.8% soil moisture, 3% atmosphere, 2.6% Marshes/swamps, 0.5% rivers, 0.25% living beings.

● Out of 0.3% surface water, lakes 84-87%, swamps make 11%, Rivers 2%

● 96.5% Seas and oceans; 1.7% groundwater, 1.7% glaciers/ice caps, <0.1% Large water bodies, <0.001% water vapour and precipitation.

● Freshwater does not mean potable water.

● Floods happen if there is excessive rainfall like a cloudburst.

● If it doesn’t rain adequately, it may lead to drought, lowering of groundwater, soil becomes dry and water becomes scarce.

● Conservation is of prime importance, so minimise the use asap.

● Collection, storage of rainwater for use in times where there is relative lack of water: Rainwater Harvesting

● Rooftop RH: Roof -> Pipes -> Storage Tank -> Filter -> Use, Recharging GW

Water cycle

● Circulation of water between ocean and land, via different states and stages.

● Evaporation: Needs energy, receives in form of heat, sunlight, warm air, happens at almost all temperature, not just boiling, from all open surfaces containing water

● Transpiration through stomata of plant leaves

● Condensation: Vapour moves up, gets cooler, form droplets, formation of clouds

Precipitation

● Outcome, condensation of water vapours in atmosphere, gravity.

● The main forms of precipitation include

○ drizzle (<0.5 mm liquid rain drops), rain, sleet (mixture of rain + partially melted snow), snow (crystalline water ice, granular material), graupel (snowflake + supercooled water droplets 2-5 mm) and hail (solid ppt, hailstone, ole, 0.5-15 cms)

● Returning to the source: Land is usually above MSL, so through gravity water goes back to sea and ocean, melting snow, rivers, streams, rain directly into ocean,

● Groundwater: Stored for quit a long time, come out via transpiration, wells, tube-wells, hand pumps,

● Run-off: If little vegetation, soil saturation or impervious surface, excess water does not seep into ground and flows over the earth’s surface. This is Soil erosion due to water.

● Rainfall: There is quantity, spatial and temporal variation both between 2 places and within the same place.

● In India, large majority of rainfall occurs during 3 months of monsoon (June-September)

● If you place clothes near a heater or under a fan, will they dry faster?

● Water drops are visible after you take out a cold bottle from the freeze.

● We breath out to make spectacles wet, vapour is at a higher temperature in our mouth, when it comes out, the temperature is lower and it condenses.

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)

● Take 2 glasses, 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.

Water vapour = 0.001 - 5 %, strong local variation, 0.25% overall earth, not included in above calculation (air is dry)

Gas % in dry air (atmosphere)Nitrogen 78.08%Oxygen 20.95%Argon 0.93CO2 0.0397 ~ 0.04Neon 0.001

Helium 0.0005Methane 0.0001

Atmospheric layers

● Troposphere (0-12 kms, 9 @ poles, 17 @ equator)

● Stratosphere (12-50 kms)

● Mesosphere (50-80 kms)

● Thermosphere (80-700 kms)

● Exosphere (700-10,000 kms)

Troposphere (Tropos- 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)

● Almost all water vapour, moisture, weather, clouds, aircrafts (especially propeller based)

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

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

Thermosphere: Mesopause to Thermopause or Exobase ● Lower half have ionosphere, temperature rises upto 15000 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

Exosphere:

● Outermost, Exobase (upper limit of thermosphere) to merging with emptiness of outer space)

● Extremely thin with ultra low density. H,He, N, H2O, CO2,

● No meteorological phenomena,

● Most satellites orbits here,

● AA + AB may overlap in upper part of thermosphere and lower part of exosphere

● S + M + Lower Th = Middle atmosphere

Air helps in :

● Photosynthesis: Takes CO2 in and produce O2

● Respiration: Takes O2 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

● 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 producers and hence replenisher of oxygen in the atmosphere.

● Inter-dependence for exchange between plants and animals for oxygen and carbon dioxide.

● Why earthworm comes out of soil in heavy rains?

Ans. Water displaces dissolved oxygen

● How will you show that air is dissolved in water?

Ans. Boiling

● Why does a lump of cotton wool shrink in water?

Ans. Air is replaced by water

Ch 16: Garbage in, Garbage out.● Lot of garbage is generated

● Safai karamcharis collect the garbage.

● Segregation: Best at source, but unfortunately done just before final disposal, useful vs non-useful, no-change vs change needed before use

● Landfill: Low lying, open area, garbage spread out, covered with soil, cycle repeats till it is full, land use conversion (in form of public parks) sans construction (at least for few decades)

● Composting, manure, rotting complete, no foul smell, provide nutrients to plants, green waste, organic waste.

● Avoid burning them rather convert them into manure.

● It is in fact illegal to burn waste especially dried leaves in various developed countries, burning generates smoke, poisonous gases and dust particles.

● Vermicomposting: Vermi- worms + Compost

● Earthworm, Farmer’s friend, red worms

● Grinding of food in “Gizzard” of earthworm

● Redworm can eat food equivalent to its own weight, daily.

● Left out dried soil-like powdery manure is vermicompost.

● Advantages

○ It has all the essential nutrients needed by plants and hence they will show amazing growth.

○ You get best out of the waste

○ You save a lot of money on harmful chemical fertilisers and insecticides

● Reduce (minimise), reuse (repeat), replace (sustainable substitute), recycle (through physical or chemical change, make it usable now)

● Use plastics judiciously. Avoid excessive and unnecessary uses, ignorant about ways of its disposal.

● Unsuitable and ill-fitted plastic, used for food storage, may lead to various disease, including cancer.

● Burning leads to highly toxic and poisonous gases being released in the environment, again leading to respiratory and other problems, including cancers.

● Swallowing by road side animals

● Choking of drain and filling of roads, even semi-floods

● Reduce (minimise both the usage as well as garbage generation)

● Reuse (repeat),

● Replace (sustainable substitute),

● Recycle (through physical or chemical change, make it usable now)

● Do not use to store food, don’t throw, don't burn plastic

● Use vermicomposting to effectively deal with kitchen waste

● Garbage disposal is as much the responsibility of government as ours.