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of Sun from reaching the Earth's surf:, ace b, absorbing them. As a result, we are Y, saved, from skin cancer., , INTR ODUC TION, Air is a mixture of several gases with major, share contributed by nitrogen (78%) and oxygen, (21 %) approximately. It is invisible, tasteless and, has no smell. The layer of air surrounding the, earth makes life possible. It is prevented from, escaping into space by gravity., , NECESSITY OF AIR, Air is a mixture of colourless gases found in, , atmosphere., , One can stay without food and water but, one cannot stay without air for a minute., Air forms a transparent medium and hence, we are able to see through it., THE ATMOSPHERE, , \, , .j, , The atmosphere, , COMPOSITION OF AIR, , The Earth is surrounded by an envelope, Air is a mixture of gases. It contains two, of air, which extends upto 200 km into space. main gases, i.e., nitrogen and oxygen. In, It is commonly called as atmosphere., addition to it, carbon dioxide and water, The envelope of air becomes thinner as, vapours are also present. Further, it contains, one moves above the Earth 's surface. Hence,, minute quantities of inert gases (helium,, mountaineers have to carry oxygen cylinders, neon, argon and krypton)., with them at higher altitudes., 5, Air also contains impurities like du i, Ozone layer is present in the stratosphere., It prevents the harmful ultraviolet radiations particles, carbon particles etc., , I, , r

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roads, the CO and CO2 content, , Percent age ol various components of air by, Table : volu, me., , 00 ~osY to we tumes given up by the, b dtle, , ,, 11, , aod a, eatbe there., jcJes, , ·~ 111ti, i, , ve~ to bf, ·ffiCtljt, o', , ,<, , I, , Pereontago, , 1., 2., 3., 4., 5., , Nitrogen, Oxygen, Carbon dioxide, Water vapour, Rare gases, , 78.09, 20.95, 0.02-0.04, , 6., , Impuritie s, , Variable, , Variable, 1.00, , ,- 1,, ,, , _, , ,I, , -::itrl, ~, , SI ', , Compon ents, , s a result of this, we find, , ,, , I ~ /j,, , the following picture represent pure air ?, 1, wnich o, , I, , ), (., I, , (-, , (i), , WhY air is not pure in the picture (a) ?, , (ii) ~~;· ~;;-, , -~i~;~;~. ·;~i.;. . . · · · · . .... . . . . . . . . . . . . . . . . . . . . . . . .... . . ., -i~. -~~-;~·. ~;. ;~~. -~-i; .~;~;i~~-~:. -~;~~. ; ; ~·. ;~~~~-~~: . . . . . . .... . . . . . .... . . . . . . . . . .., , "i~--~-~;-. ~~;~. ;~. ;-~~-, , (iii) ~~;. ~; ;-, , ·············, (a) ··················· ······· .... ······························································································, ·······., (b) ···················· .... ·········· ······· ························································································, , STUDY OF VARIOUS CONSTITUENTS, , -:, :, :, lA, A, ;- n11twu~, 2, To show that one-fifth part of air Is oxygen (0 )., Meth0 d : Fix a candle in the trough and pour water, _, into it, so th at it gets filled up to half of the level., rNote the water 1evel m, . the measuring cylinder. Now,, ight dthe candl e and cover it with the measuring, cyr, . the cylinder due, . in, . rise, in er. The water level wilt, , of oxygen. Note the level of water, e candle extinouishes., , 10, r,on, th, afterconsump, , --:::, ------_:;, , ---~==~, , ---~-------•-, , .. :::!, , ~ Water rises to one-fifth level of the cylinder, showing, that one-fifth of air is oxygen, , Result : Water rises to one-fifth level of the cylinder,, , showing that one-fifth of air is oxygen.

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bstances (Food), le)( su, Respiration, corriP, , l, l, , substances, Sir1'1P le, oxygen, , carb, , ·de+ water+ Energy, on dio)(I, , betwee, , ,.,oil, , n Breathing and Respiration, , .,arl-', , Respiration, , coflll'., , athin9, , 9re, , • g an d, . the inha~in, s of air., Jt 1, hysical, 1. thalin9, P, a, e, 11 iS, 2, · process-, , 1. It is intake of oxygen, to oxidize the food ., is a, ss, proce ., , 2. It, , chemical, , nerQY is, No heat :uring this, 3. released, , 3. It is accompanied by, , process. mes are, d for breath'ing., 4. No . enzY, require, , 4. Each breakdown step, in respiration is due to, , the release of heat, energy., , a particular enzyme., , -, , . - ~·11- /, , -F,iu,:.,, , Com".. I, .-r son between C, ombuat1on and Respiration, Combustion, Respiration1. ~;m?ustion takes place, higher temperature 1• Respiration takes place, outside the body., at body temperature, inside the body., 2. Enzymes are not, 2, required for combustion. -Enzymes are required, for respiration., 3. Combustion takes place, 3. Respiration takes place, for various fuels., for food substances, consumed by an, organism., 4. Combustion is a faster 4. Respiration is a slow, process., process., , Everyday we are using oxygen for, burning, for respiration and for various, other processes. But the amount of oxygen, in air doesn't change because the process, of photosynthesis in which oxygen 1s, released balance the used oxygen ., , ---------...., , ect to combustion, answer the following questions :, . ., ., With re Sp, . one similarity between combustion and resp1rat1on., (i) Give, , ········· ······ ··· ··· ······· ···· ·········· ···· ······································ ·····, (ii) What is that which is required for respiration but not for, , combustion ?, , 3. Photosynthesis : The process in which, green plants containing chlorophyll, with, the help of carbon dioxide, water and, , sunlight prepare their own food (glucose), and release oxygen 1s known as, Photosynthesis., Water, Carbon+, ., , dIOXide, Ct.,., , Li ght, C'hlor(lphyll, , Glucose, , + Oxygen, , 0, Energy from the sun, (sunlight), , Oxygen, , 3, , .J New T, , re nds in, , h ~ t Chemistry • 6, , Carbon dioxide, , Water, Photosynthesis by green plants, , '°', , du 1, , ~e, , Ma, , ieE, tt, fi r, , a, , I, , \

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~, , !/, , !t r-!4~ - - - - - - 7, , ~, , it't, , To show that air Is necessary for respiratio, n., Method : Take a plant and cover it with a, bell jar., Observation : The plant will remain as such, only, for few days . After few days the oxygen pres, ent in, bell jar will be used up. Hence, the plant will, shrivel, due to the lack of oxygen., Result : This due experiment proves that, air is, necessary for respiration ., , .:J, , Air is necessary for respiration, , use of other components of air, t. Carbon dioxide is needed b, plants to prepare their food by th Y&tet, ., e Pt I, of photosynthesis., r\\, 2. Nitrogen of air is used to, · used for Prov·, inert atm osphere . It ts, 1~, synthesis and also for growth of _Protei 1, 1 s1, ., ., Pant, 3. Inert gases hke he hum, are ·, ., Used ., weather forecastmg, balloons., 11, 4. Ozone layer present in atmo, · t radiatio 8Phe1, checks the harm ful uItrav1ole, t, ns fro, the sun to reach the earth., ~, 1, , RUSTING, The eating away of iron is kno, ., ., wn a1, rusting. When iron 1s, exposed to llloist .·, its surface rap1'dl y gets covered With a ¾', 1aye1, of reddish brown powdery coating. To~, coating is loose , powdery and is called ru, II., , To study the conditions of rusting, -, , Conical flask, , Iron Nails, ,~~ "-'---'A---lron Nails, ~, , (A) Only atr is pr~s~nt, (No Austtng), , ~ (B) Only water is, present, (No Rusting), , C,-, , (C) Both air and water are present, (Rusting occurs), , Flask A :, , This flas k contained only air and it showed no, rusting., ', Flask B : This flask contain, ed only water and it showed no rusting., Flask C : This flask contained water as well, as air and it showed rusting., Inference : Both air and water are essential, for rusting to take place., , Candid New Trends in !CSE Chem'·str1 ·i

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be process of crossill t, ps d. persal of seeds., l .. ne 1 a0d is, ~ A'' . ,uoll, is used to generate, 1, ,, , f~1, , ,o, , I·, , 111J ~, , !lergY, , p0 d e, , .,1jtl ., ~ jcttY., , ;. .1ectf, e, , oo1P, , ress, , ., , ed air, , is used to f'll, 1 tyres of, , (iv) Use of clean fuels can save pollution., , C •c\eS·, of photosynthesis ., .,. b', . (be process, ·, ve, s 111, 1, , ·r oelP, A', J., LJflON, O~L., . opulation, the smoke and, P, ~, w1ng, P, ~1 . tile gr0, ts released to atmosphere, w1tit, rodUC ', r111ftll P h e harmful substances are, 1, , ~~, d Tes, ., ., ., o~ illcrease · TheY cause arr pollution which, h, , av~~ pol1llcants· . r problems of the world ., ,~I f the IllaJO, , . ooe o, , (ii) Trees help to bring rain which cleans the, atmosphere., (iii), In some cars' catalytic converters are used, which convert the harmful gases into, harmless products. So we should use, catalytic converters in the cars ., , •, , •, , of Air pollution ., causes, . n is largely caused due to, . 0 uuno, (II A1r ~, of fuels which release harmful, ,1, , burning, ., during burmng., gases, . and, .n the number o f factones, . Jncrease l, ., (111, . also increase the level of au, indusmes, pollution., · g down of trees has increased the, (ill) Cuttlll, . ., levels of carbon dioxide resultmg m global, warming., , REMEDIAL MEASURES, , Nowadays. it is very important to fight air, pollu1ion, since th e number of respirato ry, diseases have increased . Headache, nausea,, 10miting, dizz iness are further associated with, airpollution. Some remedial measures which, canbetaken in this respec t are :, u) Plant more trees because trees reduce, 1h, e amount of ca rb on dioxide by, absorbin · g ll tor photosy nthesis ., Chemistry - 6, , (v) In some modern industrie s, electric, current is used to check smoke and dust, particles., (vi) Car engines nowadays, are designed to, use lead free or unleaded petrol., (vii) Reduce the use of aerosols and try to, prevent smoking., (viiz) Walk or cycle where it is safe to do so as, ', walking is free and cycling can help to, keep you fit. Spread this message, universally., (ix) Use public transport wherever you can, do it conveniently., , ~, , 5, , ( ~ ,-llu, -. u-, , ~- - - - -, , To show that air Is needed for burning., Method : Take two equal si:Zed candles, ignite them, and cover one candle with a bell jar. You will observe, that candle in the bell jar will extinguish after some, time and the other candle will keep on burning for a, longer time., , <.,-, , To show tflat, , arr is needed tor burning, , Inference : Thus, we conclude that air is necessary, for burning, the candle which is getting sufficient, amount of air burns for a longer time whereas the, candle in the bell jar extinguishes after some time.