NCERT Solutions Class 8 Science Chapter 9: The Amazing World of Solutes, Solvents, and Solutions (Hinglish)

Curiosity, Class 8 Science textbook (Reprint 2026-27), ke Chapter 9, The Amazing World of Solutes, Solvents, and Solutions, ke har sawaal ke jawaab: Probe and ponder, Activities 9.1 se 9.7 aur text ke sawaal, Keep the curiosity alive ke saare baarah sawaal, aur Discover, design, and debate. Page numbers book ke hisaab se hain (pages 134–151). Chhote notes: Chapter 9 ke notes.

Probe and ponder (page 134)

Picture mein kya ho raha hai? Gandhi aur unke saathi Dandi ke kinaare par namak ikattha kar rahe hain. Samudra ka paani namak ka paani mein vilayan hai; jab dhoop paani ko bhaap bana deti hai, ghula hua namak crystal ke roop mein reh jaata hai.

Chai mein zyada cheeni ghulna band ho gayi. Kaise theek karein? Chai cheeni se santript hai. Use garam karo, kyunki garam drav mein zyada cheeni ghulti hai, ya aur chai ya paani milaao taaki zyada vilaayak ho.

Cheeni aur namak paani mein ghulte hain par tel mein nahi: kyon? Aur paani ko achha vilaayak kyon kehte hain? Paani ke kan cheeni aur namak ke kanon ko aakarshit karke gher lete hain, unhe alag karke barabar faila dete hain; tel ke kan aisa nahi karte, isliye crystal waise hi rehte hain. Paani bahut saare padaarth ghol leta hai, isliye use achha vilaayak kehte hain.

Paani ki botalein gol ki jagah lambi aur cylinder jaisi kyon hoti hain? Cylinder pakadne aur daalne mein aasaan hai, apne samtal tale par seedha khada rehta hai, aur bina zyada khaali jagah ke saath-saath pack hota hai. Gola ludhak jaata, pakadna mushkil hota aur pack karne par beech mein jagah chhoot jaati.

Vilayan aur kitna ghulta hai (pages 135–137)

Kya Fig. 9.1 ka mishran uniform hai? Haan. Cheeni, namak aur paani uniform mishran, yaani vilayan, banaate hain. Paani mein chalk powder? Nahi, wo non-uniform mishran hai: chalk ke kan dikhte rehte hain aur neeche baith jaate hain.

Kya gaison ka mishran, jaise hawa, bhi vilayan hai? Haan. Uski gaisein barabar faili hain, isliye ye uniform mishran hai, gaison mein gaison ka vilayan.

Activity 9.1. Pehle kuch chammach namak poora ghul jaata hai; uske baad kitna bhi hilaao, kuch namak tale mein bina ghule reh jaata hai. Chammachon ki sankhya paani ki maatra par nirbhar hai, aadhe glass mein aksar chaar ya paanch. Isse pata chalta hai ki kisi taapmaan par tay maatra ka paani ek had tak hi namak ghol sakta hai: vilayan santript ho gaya.

Kis ki saandrata zyada hai: 100 mL mein 2 chammach namak, ya 50 mL mein 4 chammach? Dono ko paani ki ek hi maatra mein dekho: 50 mL mein 4 chammach = 100 mL mein 8 chammach. Isliye 50 mL mein 4 chammach zyada saandra hai.

Activity 9.2 aur paani mein gaisein (pages 137–139)

50 °C tak garam karne par bina ghule baking soda ka kya hota hai? Wo ghul jaata hai, aur phir aur daala ja sakta hai jab tak kuch dobaara na bache. 70 °C tak garam karne par bacha hua phir ghul jaata hai. Nishkarsh: zyaadatar thos padaarthon ki tarah baking soda ki ghulansheelta taapmaan ke saath badhti hai: 70 °C ka paani 50 °C se zyada gholta hai, aur 20 °C par sabse kam.

Asima Chatterjee ko aushadhiya paudhon ki or kisne kheencha? Bachpan se unhe apne pita ki tarah dawaai ke kaam aane wale paudhon mein ruchi thi, aur Bharat mein Ayurveda mein aise upchaaron ki lambi parampara hai. Rasaayanshaastri ke roop mein unhone in paudhon ke upyogi yaugikon ko nikaalne aur alag karne ke liye vilaayakon ka upyog kiya, aur mirgi aur malaria ki dawaaiyaan viksit ki.

Kya gaisein paani mein ghulti hain? Kya mishran uniform hai? Haan. Oxygen samet kai gaisein thodi maatra mein ghulti hain, aur barabar failti hain, isliye mishran uniform hai. Kya taapmaan unki ghulansheelta badalta hai? Haan: paani garam hone par gaisein kam ghulti hain, isliye thanda paani jal-jeevon ke liye zyada oxygen rakhta hai.

Buraada paani mein kyon tairta hai aur ret kyon doobti hai? Buraada paani se kam ghana hai, aur ret zyada ghani.

Ghanatva aur maap (pages 139–148)

Chaawal dhote samay bhoosi tairti hai aur chaawal doobte hain. Kyon? Bhoosi paani se kam ghani hai aur chaawal ke daane zyada ghane.

Tel ke pack par 1 litre par 910 g likha hai. Isse tel ke baare mein kya pata chalta hai? 1 litre paani ka dravyamaan lagbhag 1000 g hai. Utne hi aayatan ka tel halka hai, isliye uska ghanatva, lagbhag 0.91 g/mL, paani se kam hai, aur tel paani par tairta hai.

Activity 9.3. Watch glass rakhne ke baad balance ko tare karke zero karne par display sirf patthar ka dravyamaan dikhaata hai, jaise 16.400 g.

Chhaachh ke pack par ‘200 mL’ ka kya matlab hai? Andar ki chhaachh 200 mL, yaani 200 cm³, aayatan gherti hai.

Activity 9.4. Fig. 9.16 ka cylinder 100 mL tak naap sakta hai. Do bade nishaanon, jaise 10 mL aur 20 mL, ke beech antar 10 mL hai, aur 10 chhote bhaag hain, isliye ek bhaag 10 ÷ 10 = 1 mL hai. Ye sabse chhota aayatan 1 mL padh sakta hai.

Measuring cylinder beaker ki tarah chaude aur chhote ki jagah patle aur lambe kyon hote hain? Patli nali mein aayatan ka chhota badlaav bhi drav ki oonchaai ko saaf badalta hai, isliye nishaan door-door hote hain aur sateekta se padhe jaate hain. Chaude bartan mein star mushkil se hilta.

Activity 9.5. Rangeen drav ka star kaise padhte hain? Meniscus ke upari hisse par; paani aur rangheen dravon ke liye nichle hisse par, aankh sateh ke star par rakhkar.

Activity 9.6. Notebook: 25 cm × 18 cm × 2 cm = 900 cm³. Joote ka dibba ya paasa bhi isi tarah, lambaai × chaudaai × oonchaai se naapa jaata hai.

Activity 9.7 (Table 9.2). Patthar: shuruaat 50 mL, ant 55 mL, hataaya gaya paani 5 mL, isliye patthar ka aayatan 5 cm³ hai. Dhaatu ki chaabi ya koi aur cheez isi tarah likhi jaati hai; chhoti chaabi aksar star ko sirf 1 ya 2 mL badhaati hai. Patthar ka ghanatva: 16.400 g ÷ 5 cm³ = 3.28 g/cm³.

Think like a scientist: doobte ande ko kaise tairaayein? Paani mein bahut saara namak gholo. Namak ka paani ande se zyada ghana ho jaata hai, isliye anda upar aakar tairta hai.

Keep the curiosity alive (pages 149–151)

1. (i) Galat. Oxygen garam paani se zyada thande paani mein ghulti hai. (ii) Galat. Ret aur paani non-uniform mishran hai, vilayan nahi. (iii) Galat. Kisi cheez dwaara ghera gaya sthaan uska aayatan hai, dravyamaan nahi. (iv) Galat. Usi taapmaan par asantript vilayan mein santript se kam vilay ghula hota hai. (v) Sahi.

2. (i) immersed (duboya/utaara); rise (badhat). (ii) solute (vilay); fixed quantity (100 mL) of solvent (vilaayak ki tay maatra). (iii) decreases (ghatta hai). (iv) saturated (santript).

3. (ii): paani tel se zyada ghana hai, isliye tel us par tairta hai.

4. Ghanatva = 225 g ÷ 90 cm³ = 2.5 g/cm³. Ye paani ke 1 g/cm³ se zyada hai, isliye moorti doob jaayegi.

5. (iii) sabse uchit hai: us taapmaan par santript vilayan mein aur vilay nahi ghulta. (i) galat hai, kyunki santript vilayan apni had tak pahunch chuka hai. (ii) galat hai, kyunki ye santript vilayan ka varnan hai; asantript ab bhi aur ghol sakta hai. (iv) galat hai, kyunki koi bhi vilayan kisi bhi taapmaan par santript ho jaata hai jab wo jitna ghol sakta hai utna vilay rakh le.

6. 2 litre = 2000 mL, isliye botal 2000 − 500 = 1500 mL (1.5 L) aur rakh sakti hai.

7. Ghanatva = 400 g ÷ 40 cm³ = 10 g/cm³.

8. Chhilka spongy hai aur nanhi hawa ki jebon se bhara hai, isliye chhilke wala poora santra paani se kam ghana hai aur tairta hai. Chhilka hataane par phal paani se zyada ghana hai aur doob jaata hai.

9. A: 200 ÷ 40 = 5 g/cm³. B: 240 ÷ 60 = 4 g/cm³. Cheez A zyada ghani hai, bhale B bhaari hai.

10. Mitti ka ghanatva 120 g ÷ 60 cm³ = 2 g/cm³ hai, aur chapta karne ke baad bhi 2 g/cm³ rehta hai. Aakaar badalne se na dravyamaan badalta hai na aayatan.

11. Aayatan = dravyamaan ÷ ghanatva = 600 ÷ 7.9 ≈ 75.9 cm³.

12. Glass ki nali mein paani ka uthna dikhaata hai ki test tube ka paani garam hone par failta hai: uska aayatan badhta hai jabki dravyamaan wahi rehta hai. Isliye uska ghanatva ghatta hai.

Discover, design, and debate (page 151)

Dead Sea: iska paani bahut khaara hai, samudra se lagbhag das guna, aur itne saandra vilayan mein machhliyaan aur paudhe zinda nahi reh sakte; sirf kuch sookshmjeev rehte hain. Khaara paani itna ghana bhi hai ki log us par aasaani se tairte hain. Aisi doosri khaari jheelein hain USA ki Great Salt Lake aur Djibouti ki Lake Assal. Alag vilaayakon mein namak: namak paani mein achhi tarah ghulta hai, sirke mein bhi ghulta hai jo zyaadatar paani hai, aur tel mein lagbhag nahi ghulta. Debate: paani kisi bhi aam drav se zyada padaarth gholta hai, isliye khaana banaane, safaai, dawaai aur hamare shareer ke andar itna kaam aata hai; par wo tel, grease ya mom nahi ghol sakta, jinke liye doosre vilaayak chahiye, isliye wo bahut upyogi hai par sab kuch ghol nahi sakta.

Hamari vaigyanik virasat, Ningel ka namak. Manipur ke Thoubal zile ke Ningel gaon mein puraane kuon ka khaara paani lakdi ki aag par dhaatu ke bartanon mein tab tak ubaala jaata hai jab tak paani bhaap na ban jaaye aur namak ke crystal na ban jaayein; namak ko kele ke patton se gol cake ka aakaar diya jaata hai aur phanek kapde mein lapeta jaata hai.