NCERT Solutions Class 8 Science Chapter 7: Particulate Nature of Matter (Hinglish)

Chapter 7, Particulate Nature of Matter, Curiosity, Class 8 Science textbook (Reprint 2026-27) ke har sawaal ke jawaab: Probe and ponder ke sawaal, har activity ke sawaal, Think like a scientist, Keep the curiosity alive ke dason sawaal, aur Discover, design, and debate. Page number book ke hisaab se hain (pages 98–115). Chhote notes: Chapter 7 ke notes.

Probe and ponder (page 98)

Hum pathar ya ret ka dher laga sakte hain, par paani ka kyun nahi? Pathar aur ret ke daane solid hain: unke kan tay jagah par jude hain, isliye har tukda apna aakaar rakhta hai aur tukde ek doosre par tik sakte hain. Paani liquid hai, jiske kan ek doosre ke paas se khisakte hain, isliye wo dher banne ki jagah beh jaata hai.

Paani judi hatheliyon ka aakaar kyun leta hai aur chhodne par kho deta hai? Liquid ka aakaar tay nahi hota; wo jo use thaame uska aakaar le leta hai. Hatheliyan khulte hi use koi nahi thaamta, isliye wo beh jaata hai.

Na dikhne waali hawa gubbaare ka vajan kaise badhaati hai? Hawa padaarth hai. Wo aise kanon se bani hai jinka dravyamaan hota hai, aur zyaada hawa ke kanon se bhara gubbaara khaali gubbaare se thoda bhaari hota hai.

Kya hum aaj wahi hawa saans mein lete hain jo hazaaron saal pehle thi? Iske kan nasht nahi hote; ve hawa, paani, mitti aur jeevon ke beech ghoomte rehte hain, isliye hamaari saans ki hawa ke bahut se kan bahut lambe samay se maujood hain, haalaanki samay ke saath gason ka mishran thoda badalta hai.

Activity 7.1 aur 7.2 (pages 99–100)

Kya chalk powder ka har kan ab bhi chalk hai? Haan. Todna aur peesna bhautik parivartan hai; sirf tukdon ka size badalta hai. Kya ye kan chalk ki sabse chhoti ikaai hain? Nahi: siddhaant mein inhe aur peesa ja sakta hai jab tak aisi ikaaiyan na mil jaayein jo toot na sakein, yaani chalk ke constituent kan.

Paani mein cheeni. Hilaane se pehle upar ki parat meethi nahi lagti; hilaane ke baad lagti hai. Cheeni ke kan dikhte nahi, par swaad batata hai ki cheeni wahan hai. Cheeni kahan gayi? Wo apne constituent kanon mein toot gayi, jo paani ke kanon ke beech ki jagah mein fail gaye.

Activity 7.3 aur solid avastha (pages 101–103)

Nirikshan. Lohe ki keel, sendha namak, pathar, lakdi, chaabi aur aluminium, sab apna aakaar aur size rakhte hain: ye solid hain, jinke kan tagde se jude hain. Hathaude se maarne par dhaatu ki cheezein mud ya chapti ho jaati hain par ek tukda rehti hain, pathar takkar jhel leta hai, sendha namak toot jaata hai aur lakdi mein gaddha padta hai. Kya solid ke kanon ko door karne ka koi tareeka hai? Haan, garam karke: melting point par ve itni zor se kaanpte hain ki apni jagah chhod dete hain aur solid liquid ban jaata hai. Liquid aur gas ka kya? Liquid ka aayatan tay hai; gas ka nahi.

Activity 7.4 aur liquid avastha (pages 103–105)

Nirikshan. Paani har bartan ka aakaar leta hai, par uska star 200 mL hi rehta hai. Kya tum paani mein ungli chala sakte ho? Haan, use hamesha ke liye kaate bina; ungli ke peechhe paani phir jud jaata hai, jo dikhaata hai ki liquid mein aakarshan solid se kam hai par kanon ko paas rakhta hai. Gira hua paani har taapmaan par kyun gaayab ho jaata hai? Evaporation ki wajah se: boiling point se neeche bhi kuch kan satah se dheere dheere nikalte rehte hain.

Activity 7.5 aur gas avastha (pages 105–106)

Kya gas ka aayatan tay hota hai? Nahi. Kaanch ki plate hatate hi Gas Jar A mein band dhuaan Gas Jar B mein bhar jaata hai aur dono jars ka aakaar le leta hai. Gas ke kan har disha mein aazaadi se chalte hain aur aakarshan lagbhag nahi hota, isliye gas ka na aakaar tay hai na aayatan.

Activity 7.6 aur 7.7: kanon ke beech jagah (pages 107–109)

Hawa waali syringe. Plunger dabaane par hawa ka aayatan ghatta hai: gas dab sakti hai, kyunki uske kanon ke beech kaafi jagah hoti hai; chhodne par plunger waapas aa jaata hai. Paani ke saath plunger lagbhag nahi hilta: paani lagbhag incompressible hai.

Cheeni aur paani ka star. Anumaan aur nateeja: cheeni daalne par star A se B tak badhta hai aur ghulne par B se thoda neeche aa jaata hai (C), kyunki cheeni ke kan paani ke kanon ke beech ki jagah gher lete hain. Namak ya glucose ke saath bhi aisa hi hota hai. Ret ya pathar ke tukdon ke saath kuch nahi ghulta; tukde neeche baith kar jagah gherte hain, isliye star badhta hai aur badha hi rehta hai. Cheeni ghulti hai par ret kyun nahi? Paani ke kan cheeni ke kanon ko alag kar lete hain, par ret ke kan aapas mein bahut tagde jude hote hain. Solid mein jagah: solid ke kan kase hote hain, par unke beech bhi chhoti jagah rehti hai, jisme kuch nahi hota.

Activity 7.8 aur 7.9: chalte kan (pages 109–111)

Paani mein potassium permanganate. Daanon se gulaabi dhaariyan nikalti hain, aur kuch der mein poora glass ek jaisa gulaabi ho jaata hai, kyunki chalte paani ke kan daanon se kan kheench kar unhe failaate hain. Think like a scientist: rang garam paani mein sabse tez, kamre ke taapmaan par dheere aur barf jaise thande paani mein sabse dheere failta hai, kyunki garmi se kan tez chalte hain; neeche ka diagram ye dikhaata hai.

Agarbatti. Haan, khushboo jald hi poore kamre mein aa jaati hai: chalte hawa ke kan uske kanon ko har jagah le jaate hain. Aur udaaharan: rasoi mein pakte khaane ki khushboo doosre kamre tak pahunchna, door se perfume ya phoolon ki khushboo aana, cooking gas cylinder leak hone ki gandh, aur aag ka dhuaan failna.

Keep the curiosity alive (pages 113–114)

1. (iv) Solid mein kan paas paas jude hote hain aur liquid mein ek doosre ke paas se khisakte hain.

2. (i) Sahi. (ii) Sahi: pighalte samay kan thoda door hote hain aur unke beech aakarshan ghatta hai. (iii) Sahi. (iv) Sahi. (v) Sahi. (vi) Galat. Sahi kathan: garam karne par kapoor ke kan urja paakar vaashp ban jaate hain; ye kan hawa mein fail jaate hain, aur inhi ki gandh hume aati hai.

3. (iii) Kursi ka kuch nahi bachega, kyunki kursi, har padaarth ki tarah, poori tarah apne constituent kanon se bani hai.

4. Gas ke kanon mein aakarshan lagbhag nahi hota, unke beech badi jagah hoti hai, aur ve aazaadi se aur tez chalte hain, isliye do gas aasaani se ek doosre mein fail jaati hain. Solid ke kan tay jagah par kase hote hain aur sirf kaanp sakte hain, isliye ve doosre solid mein nahi ja sakte.

5. Doodh liquid hai: uske kan ek doosre ke paas se khisak sakte hain, isliye wo bahkar table par fail jaata hai. Glass ka tumbler solid hai: tagda aakarshan uske kanon ko tay jagah par rakhta hai, isliye wo apna aakaar banaaye rakhta hai.

6. Barf mein kan ek niyamit pattern mein jude hote hain aur sirf kaanpte hain; pighalne par paani ke kan paas par bikhre hote hain aur ek doosre ke paas se khisakte hain; paani ubalne par vaashp ke kan door door hote hain aur aazaadi se chalte hain.

7. Aluminium foil (solid): kan qataaron mein kase hue. Glycerin (liquid): kan paas paas par bina kisi tay kram ke. Methane (gas): kuch kan, door door.

8. Mombatti ka shareer aur uske kinaaron par jami boondein solid wax hain (kase hue kanon waali banaavat). Batti ke aas paas pighle wax ka taalaab liquid wax hai (paas par bikhre kanon waali banaavat). Batti se uthta dhuaan wax ki vaashp, yaani gas avastha, le jaata hai (door door kanon waali banaavat).

9. Samudr ke paani ka namak ghula hua hai: wo apne constituent kanon mein toot kar paani ke kanon ke beech fail gaya hai. Ye kan dikhne ke liye bahut chhote hain, par jeebh inka swaad pehchaan leti hai.

10. Ye solid hain. Chaawal ke har daane aur aate ke har kan ka apna tay aakaar aur aayatan hai. Dher jar ka aakaar sirf isliye leta hai kyunki bahut se chhote solid tukde ek doosre par fisal sakte hain; tukde khud liquid ki tarah nahi behte, aur chaawal ka dher bhi lagaaya ja sakta hai, jo paani ka nahi lagta.

Discover, design, and debate (page 115)

Garam paani mein bottle par gubbaara: gubbaara phool jaata hai, kyunki garam hawa ke kan tez chalte hain aur fail jaate hain, isliye hawa zyaada jagah gherti hai; thanda hone par phir sikud jaata hai. Model: solid ke liye mitti ki goliyan ya moti dabbe mein kas kar rakho, liquid ke liye dheela dher banaao aur gas ke liye kuch goliyan door door failaao. Role-play: solid ban kar paas paas khade ho kar apni jagah jhoolo, liquid ban kar paas rehte hue idhar udhar khisko, aur gas ban kar poore kamre mein tezi se ghoomo, ‘taapmaan’ badhne par aur tez. Debate, ‘gas saari uplabdh jagah bhar deti hai’: faaydemand, kyunki oxygen kamre ke har kone tak pahunchti hai, gandh hume gas leak ya aag se saavdhaan karti hai, aur hawa tyre aur gubbaaron ko ek samaan bharti hai; nuksaandeh, kyunki zehreeli gas, dhuaan aur pradooshit hawa bhi tezi se failte hain.

Chhote notes aur zyaada practice topic pages par hain: padaarth ki avasthaayein, kanon ke beech doori aur gati aur padaarth kis cheez se bana hai?