Pure Substance Kya Hai? Science wala “Shuddh”
Packet pe “100% pure” likha hai, par kya woh science ki nazar mein bhi pure hai? 🔬
🧭 Is Post Mein
📖 Kahani: “Pure” ka Asli Matlab
Sunday subah Priya ki mummy dairy se doodh ka packet laayin. Packet pe bade akshar mein likha tha: “100% Pure Doodh”.
Golu ne turant kaha: “Pichli post mein humne padha tha ki doodh mein paani, vasa (fat), protein sab mila hota hai. Toh doodh mixture hai. Phir yeh ‘pure’ kaise?”
Rohan soch mein pad gaya: “Matlab packet jhooth bol raha hai?”
Priya ki didi, jo college mein chemistry padhti hai, muskurayi: “Nahi, packet sach bol raha hai, par dukaan wali bhasha mein. Dukaan wala ‘pure’ ka matlab hai: isme koi milawat nahi. Science wala ‘pure’ ka matlab bilkul alag hai.”
Toh aaj hum yahi samjhenge: science mein pure substance kise kehte hain, aur use pehchante kaise hain. 🔍
🎯 Is Post Mein Kya Seekhenge
- Roz ki bhasha ka “pure” (milawat nahi) aur science ka “pure” kaise alag hain
- Pure substance ki pehchaan: ek hi tarah ke kan, fixed composition, fixed gun
- Pure substance ko physical tareekon se alag nahi kar sakte, mixture ko kar sakte hain
- Fixed melting point aur boiling point se purity kaise jaanchte hain
- Pure substance ke do prakar: elements aur compounds (sirf parichay)
🧱 Basics: Pehle Yeh Aana Chahiye
1. Mixture: do ya zyada cheezon ka mel, jisme har cheez apne gun rakhti hai aur unhe alag kiya ja sakta hai. (Post 1: Mixture Kya Hai?)
2. Uniform aur non-uniform mixture: jisme hisse har jagah barabar faile hon (cheeni ka ghol) ya barabar na faile hon (mitti wala paani). (Post 2: Mixtures ke Prakar)
3. Kan (particles): har cheez bahut-bahut chhote kanon se bani hai, jo aankh se nahi dikhte.
4. Physical tareeke: chhanna (filtration), bhaap banana (evaporation), magnet se kheenchna, chunna (handpicking). Inme koi nayi cheez nahi banti.
💡 Concept: Science mein “Pure” ka Matlab
1️⃣ Do tarah ka “pure”
Isliye yeh matlab sehat ke liye zaroori hai: milawat wala khana nuksaan kar sakta hai.
Doodh mein paani, vasa, protein, cheeni (lactose) jaise kai tarah ke kan hain. Isliye bina milawat ka doodh bhi science mein mixture hi hai.
2️⃣ Pure substance ki 4 pehchaan
Mixture mein yeh sab nahi hota: namak ke ghol mein namak kam-zyada daal sakte ho, isliye uski banawat tay nahi, aur uska boiling point bhi 100°C se upar chala jaata hai.
3️⃣ Physical tareeke se alag nahi hota
Namak ke ghol ko garam karo, paani bhaap ban kar ud jaata hai aur namak bach jaata hai. Matlab ghol do cheezon mein toot gaya, isliye woh mixture hai. Par shuddh namak ko chhano, garam karke sukhao, magnet lagao, kuch bhi karo, woh namak hi rahega. Isliye namak pure substance hai.
4️⃣ Pure substance ke do prakar
- Element (tatva): sabse saral pure substance, jise kisi bhi tareeke se aur saral cheezon mein nahi toda ja sakta. Jaise tamba (copper), aluminium, sona, oxygen, carbon. Iske baare mein Post 4 mein padhenge.
- Compound (yaugik): do ya zyada elements ke chemical tareeke se, ek tay anupaat mein judne se bana pure substance. Jaise paani, namak, cheeni, baking soda. Iske baare mein Post 5 mein padhenge.
Toh kahani wali photo ka jawab: tambe ka taar aur aluminium foil elements hain; cheeni aur namak compounds hain (agar shuddh hon). Glass ka nal wala paani? Usme ghule hue namak (salts) hote hain, isliye woh mixture hai. Sirf distilled paani pure hai.
🖼️ Diagrams: Picture se Samjho
🔐 Deep Concept: Uniform dikhna ≠ Pure hona
Bahut bachche sochte hain: “jo cheez ek jaisi dikhe, woh pure hai.” Yeh galat hai. Cheeni ka ghol, hawa, sirka aur brass sab uniform dikhte hain, par sab mixture hain.
Toh asli farq kya hai? Socho kan ke level pe:
Purity jaanchne ka scientist wala test: melting point ya boiling point naapo. Agar padarth ek tay tapmaan pe pighle ya ubale, aur poora pighalne tak tapmaan wahi rahe, toh woh pure hone ki sambhavna bahut zyada hai. Agar tapmaan thoda kam-zyada ho ya badalta rahe, toh usme koi aur cheez mili hai.
Isiliye sadkon pe sardiyon mein baraf hatane ke liye namak daala jaata hai (thande deshon mein): namak milne se baraf 0°C se kam tapmaan pe bhi pighal jaati hai. Mixture ka melting point badal gaya!
✏️ Examples: Pure Substance hai ya Mixture?
| Cheez | Jawab | Kyun? |
|---|---|---|
| Distilled paani | Pure (compound) | Sirf paani ke kan |
| Nal ka / kuen ka paani | Mixture | Paani mein ghule salts aur gases |
| Cheeni (sucrose) | Pure (compound) | Ek hi tarah ke kan |
| Doodh | Mixture | Paani, vasa, protein, lactose |
| Tambe ka taar | Pure (element) | Sirf copper |
| 24 carat sona | Lagbhag pure (element) | Lagbhag sirf sona |
| 22 carat sona (gehne) | Mixture (alloy) | Sone mein tamba/chandi milayi |
| Hawa | Mixture | Nitrogen, oxygen, CO₂ aur kai gases |
| Oxygen gas (cylinder wali shuddh) | Pure (element) | Sirf oxygen |
| Ghee, shahad (honey) | Mixture | Kai tarah ki cheezein mili hain |
| Baking soda | Pure (compound) | Ek hi padarth: sodium hydrogen carbonate |
| Heera (diamond) | Pure (element) | Sirf carbon |
⚖️ Difference Table: Pure Substance vs Mixture
| Baat | Pure Substance | Mixture |
|---|---|---|
| Kan | Sirf ek tarah ke | Do ya zyada tarah ke |
| Banawat (composition) | Tay (fixed) | Kam-zyada ho sakti hai |
| Gun | Har jagah same | Hisson ke gun alag-alag dikh sakte hain |
| Melting / boiling point | Fixed | Fixed nahi, ek range mein |
| Physical tareeke se alag karna | Nahi ho sakta | Ho sakta hai |
| Examples | Distilled paani, namak, tamba | Doodh, hawa, nal ka paani |
Roz ka “pure” vs science ka “pure”:
| Roz ki bhasha | Science ki bhasha |
|---|---|
| Milawat nahi hai | Sirf ek hi padarth hai |
| “Pure ghee”, “pure doodh” sahi hain | Ghee aur doodh dono mixture hain |
| Quality aur sehat ki baat | Kan aur banawat ki baat |
🚫 Misconceptions: Log aisa sochte hain… lekin
✅ Packet ka matlab “milawat nahi”. Science ka matlab “sirf ek padarth”. Pure doodh bhi mixture hai.
✅ Saaf nal ke paani mein bhi namak (salts) ghule hote hain jo dikhte nahi. Sirf distilled paani pure hai.
✅ Uniform mixture mein do tarah ke kan hain (bas barabar faile hain). Pure mein ek hi tarah ke.
✅ Compound bhi pure substance hai, chahe usme do ya zyada elements jude hon (jaise paani mein hydrogen aur oxygen).
✅ Doodh, daal, ORS, hawa sab mixture hain aur zaroori hain. “Mixture” koi buri cheez nahi, bas ek prakar hai.
🔤 Key Terms (Exam mein English shabd hi likhna)
❓ FAQs
Kya “pure doodh” likhna galat hai?
Nahi. Dukaan ki bhasha mein iska matlab hai ki doodh mein milawat nahi. Bas science ki bhasha mein doodh ek mixture hai. Dono apni jagah sahi hain.
RO ya filter ka paani pure hai kya?
Nahi. RO bahut saare salts hata deta hai, par kuch minerals phir bhi rehte hain (aur peene ke liye kuch minerals achhe bhi hain). Science wala pure paani distilled paani hai.
Distilled paani kaise banta hai?
Paani ko ubal kar bhaap banate hain, phir us bhaap ko thanda karke wapas paani banate hain. Ghule hue salts bhaap nahi bante, isliye peeche reh jaate hain. Jo paani milta hai woh shuddh hota hai.
Kya sab pure substances element hote hain?
Nahi. Pure substance do tarah ke hote hain: elements (jaise tamba) aur compounds (jaise paani, namak). Dono mein ek hi tarah ke kan hote hain.
Pahaad pe paani 100°C se pehle kyun ubal jaata hai? Kya woh pure nahi?
Woh pure hi hai. Boiling point hawa ke dabaav pe bhi depend karta hai. Pahaad pe hawa ka dabaav kam hota hai, isliye shuddh paani wahan 100°C se kam pe ubalta hai. Isliye hum kehte hain “normal hawa ke dabaav (samudra-tal) pe 100°C”. Ek hi jagah aur ek hi dabaav pe pure paani ka boiling point hamesha same rahega.
Fixed boiling point se purity kaise pata chalti hai?
Shuddh padarth hamesha ek hi tapmaan pe ubalta hai. Agar usme kuch mila ho toh boiling point badal jaata hai. Toh tapmaan naap kar pata chal sakta hai ki koi aur cheez mili hai ya nahi.
🧪 Activity (NCERT): Pure Hai ya Mixture? Chhaanbeen Karo
NCERT book mein is section ke saath ek sochne wala kaam hai: kuch roz ki cheezon (doodh, packet wala fruit juice, baking soda, cheeni aur mitti) ko “pure substance” ya “mixture” mein baantna. Ise detective ki tarah karo:
Answers dekho (pehle khud bharna!)
| Cheez | Jawab | Kaaran |
|---|---|---|
| Doodh | Mixture | Paani, vasa, protein, lactose: kai padarth |
| Packet wala fruit juice | Mixture | Paani, fal ka ras, cheeni, aur kai cheezein |
| Baking soda | Pure substance (compound) | Ek hi padarth: sodium hydrogen carbonate |
| Cheeni | Pure substance (compound) | Ek hi padarth: sucrose |
| Mitti | Mixture | Reth, chikni mitti, sadi pattiyan, paani, hawa |
Is activity se kya seekha? Kisi cheez ko “pure” kehne se pehle socho ki usme kitne padarth hain. Roz ki zyada tar cheezein mixture hi hain!
Yeh activity NCERT ki Class 8 Science book Curiosity (Chapter 8) par aadharit hai, aur yahan apne shabdon mein samjhayi gayi hai.
🏠 Mini Experiments (Ghar pe)
Result: namak wali jagah saaf safed parat dikhegi. Nal ke paani wali jagah bhi halka safed gol nishaan dikh sakta hai. Matlab paani mein kuch ghula tha, toh woh mixture hai. (Pure paani ud jaane ke baad kuch nahi chhodta.)
Result: sirf paani wali katori pehle jamegi. Namak wala paani der se jamta hai (aur kabhi-kabhi poora jamta bhi nahi), kyunki use jamne ke liye 0°C se zyada thand chahiye. Yeh dikhata hai ki mixture ka freezing point pure paani (0°C) jaisa nahi rehta.
Rasoi se 5 packet uthao (namak, cheeni, biscuit, masala, ketchup). Har ek ki ingredients list padho. Jisme sirf ek cheez likhi ho, use “pure ho sakta hai” group mein, baaki ko “mixture” group mein rakho.
Dhyan do: iodised namak mein namak ke saath thoda iodine wala padarth milaya jaata hai, isliye science ki nazar mein woh bhi ek mixture hai!
🧠 Think Like a Scientist
🌍 Real Life Mein Pure Substances
- Dawaiyan aur injection: dawaiyon mein bahut shuddh padarth aur distilled jaisa shuddh paani use hota hai, kyunki zara si milawat bhi nuksaan kar sakti hai.
- Car aur inverter ki battery: isme distilled paani daala jaata hai, nal ka nahi, kyunki nal ke paani ke salts battery ko kharab kar dete hain.
- Sunaar ki dukaan: 24 carat sona lagbhag shuddh hota hai, par bahut naram hota hai. Isliye gehne 22 carat (sone ka mixture) se banate hain, jo zyada mazboot hota hai.
- Hospital ki oxygen: mareez ko shuddh oxygen cylinder se di jaati hai.
- Food check karna: sarkari labs milawat (adulteration) jaanchti hain taaki “pure” likha khana sach mein bina milawat ka ho.
🔁 Recap: Poora Post Ek Nazar Mein
- Roz ka “pure” = milawat nahi. Science ka “pure” = sirf ek padarth, ek hi tarah ke kan.
- Pure substance ki banawat tay hoti hai aur gun har jagah same hote hain.
- Pure substance ko physical tareekon se alag nahi kar sakte; mixture ko kar sakte hain.
- Pure substance ka melting aur boiling point fixed hota hai (shuddh paani: 0°C pe jamta, 100°C pe ubalta, normal hawa ke dabaav pe).
- Uniform dikhna pure hone ka saboot nahi (cheeni ka ghol uniform hai par mixture hai).
- Pure substance ke do prakar: elements (tamba, oxygen) aur compounds (paani, namak, cheeni).
✍️ Fill in the Blanks
1. Science mein pure substance mein sirf ______ tarah ke kan hote hain.
ek
2. Roz ki bhasha mein “pure” ka matlab hai ki usme ______ nahi hai.
milawat (adulteration)
3. Shuddh paani normal hawa ke dabaav pe ______ °C pe ubalta hai.
100
4. Pure substance ki composition ______ hoti hai.
tay (fixed)
5. Pure substance ke do prakar hain: elements aur ______.
compounds
6. Bhaap ko thanda karke banaya gaya shuddh paani ______ paani kehlata hai.
distilled (aasvit)
✅ True / False
1. “Pure doodh” science ki nazar mein ek pure substance hai.
False: doodh mein paani, vasa, protein jaise kai padarth hain, isliye woh mixture hai.
2. Cheeni ek pure substance hai.
True: shuddh cheeni mein sirf sucrose ke kan hote hain.
3. Har uniform mixture ek pure substance hota hai.
False: uniform mixture mein do tarah ke kan barabar faile hote hain, jaise cheeni ka ghol.
4. Pure substance ko chhaan kar ya bhaap bana kar do cheezon mein alag kiya ja sakta hai.
False: physical tareeke se pure substance alag nahi hota; yeh mixture ki pehchaan hai.
5. Namak milane se paani ka boiling point 100°C se badh jaata hai.
True: mixture banne se boiling point badal jaata hai; namak wala paani 100°C se upar ubalta hai.
6. Compound bhi ek pure substance hai.
True: compound mein ek hi tarah ke kan hote hain aur banawat tay hoti hai, jaise paani.
🔘 MCQs
Q1. Inme se science ki nazar mein pure substance kaun sa hai? (a) Doodh (b) Hawa (c) Distilled paani (d) Nal ka paani
✅ (c) Distilled paani: sirf paani ke kan.
(a) doodh mein kai padarth hain, mixture.
(b) hawa mein kai gases hain, mixture.
(d) nal ke paani mein salts ghule hain, mixture.
Q2. Packet pe “pure ghee” ka matlab kya hai? (a) Ghee mein sirf ek tarah ke kan hain (b) Ghee mein milawat nahi hai (c) Ghee ek element hai (d) Ghee ek compound hai
✅ (b): yeh roz ki bhasha ka “pure” hai.
(a) galat: ghee kai tarah ki vasa (fats) ka mixture hai.
(c) ghee element nahi hai.
(d) ghee ek akela compound nahi, kai padarthon ka mel hai.
Q3. Pure substance ki pehchaan kaun si NAHI hai? (a) Fixed composition (b) Fixed boiling point (c) Physical tareeke se alag ho jaana (d) Ek hi tarah ke kan
✅ (c): physical tareeke se alag hona mixture ki pehchaan hai.
(a), (b), (d) teeno pure substance ki sahi pehchaan hain.
Q4. Inme se kaun sa element hai? (a) Namak (b) Tamba (copper) (c) Cheeni (d) Paani
✅ (b) Tamba: sirf copper se bana.
(a) namak sodium aur chlorine ka compound hai.
(c) cheeni carbon, hydrogen, oxygen ka compound hai.
(d) paani hydrogen aur oxygen ka compound hai.
Q5. Ek safed powder kisi ek tay tapmaan pe nahi pighalta, balki tapmaan badalte-badalte dheere-dheere pighalta hai. Iska matlab? (a) Woh pure hai (b) Usme koi aur cheez mili hai (c) Woh element hai (d) Woh gas hai
✅ (b): fixed melting point na hona milawat ka sanket hai.
(a) pure substance ek tay tapmaan pe pighalta hai.
(c) element bhi pure hota hai, toh uska bhi melting point fixed hota.
(d) powder thos hai, gas nahi.
Q6. Cheeni ka ghol uniform dikhta hai, phir bhi mixture hai kyunki: (a) Usme do tarah ke kan hain (b) Woh meetha hai (c) Woh transparent hai (d) Usme koi nayi cheez bani hai
✅ (a): cheeni aur paani dono ke kan hain.
(b) meetha hona mixture ka kaaran nahi.
(c) distilled paani bhi transparent hai aur pure hai.
(d) ghol banane mein koi nayi cheez nahi banti.
Q7. Gehne 22 carat sone se kyun banate hain? (a) 22 carat sona pure element hai (b) 24 carat sona bahut naram hota hai, mixture zyada mazboot hai (c) 22 carat sona compound hai (d) 24 carat sona chamakta nahi
✅ (b): sone mein tamba/chandi milane se woh mazboot ho jaata hai.
(a) 22 carat sona mixture (alloy) hai.
(c) alloy compound nahi, mixture hai.
(d) 24 carat sona bhi khoob chamakta hai.
Q8. Battery mein nal ki jagah distilled paani kyun daalte hain? (a) Distilled paani sasta hai (b) Nal ke paani ke ghule salts battery ko nuksaan karte hain (c) Distilled paani mein namak hota hai (d) Nal ka paani jam jaata hai
✅ (b): distilled paani mein koi ghuli cheez nahi hoti.
(a) sasta hona kaaran nahi.
(c) ulta: distilled paani mein namak nahi hota.
(d) nal ka paani normal tapmaan pe nahi jamta.
🔗 Assertion–Reason
Options: (a) A aur R dono sahi, aur R, A ko samjhata hai · (b) A aur R dono sahi, par R, A ko nahi samjhata · (c) A sahi, R galat · (d) A galat, R sahi
1. A: Distilled paani ek pure substance hai. R: Distilled paani mein sirf ek tarah ke kan hote hain.
✅ (a): ek hi tarah ke kan hona hi pure hone ka kaaran hai.
2. A: Packet wala “pure doodh” science mein pure substance hai. R: Us doodh mein koi milawat nahi ki gayi.
✅ (d): A galat hai (doodh mixture hai). R sahi ho sakta hai, par bina milawat ka hona science wala pure hona nahi hai.
3. A: Namak ka ghol uniform hai. R: Namak ka ghol ek pure substance hai.
✅ (c): A sahi hai (namak barabar ghula hai). R galat hai: ghol mein paani aur namak do padarth hain, toh woh mixture hai.
📝 Very Short Answer (1 mark)
1. Science mein pure substance kise kehte hain?
Jo padarth sirf ek hi tarah ke kanon se bana ho aur jise physical tareekon se alag padarthon mein na toda ja sake.
2. Pure substance ke do prakar likho.
Elements aur compounds.
3. Shuddh baraf kis tapmaan pe pighalti hai?
0°C pe.
4. Ek element aur ek compound ka naam likho.
Element: tamba (copper). Compound: paani.
5. “Adulteration” ka Hinglish matlab kya hai?
Milawat: kisi cheez mein sasti ya kharab cheez milana.
📝 Short Answer (2–3 marks)
1. Roz ki bhasha ke “pure” aur science ke “pure” mein farq likho, ek example ke saath.
Roz ki bhasha mein pure ka matlab hai: milawat nahi, jaise “pure doodh”. Science mein pure ka matlab hai: sirf ek padarth, ek tarah ke kan. Isliye pure doodh roz ki bhasha mein pure hai, par science mein mixture hai (paani, vasa, protein, lactose).
2. Nal ka paani mixture kyun hai aur distilled paani pure kyun?
Nal ke paani mein paani ke saath salts aur gases ghule hote hain; ise ubal kar udaao toh safed nishaan bachta hai. Distilled paani bhaap ko thanda karke banta hai, isme sirf paani ke kan hote hain, isliye pure hai.
3. Boiling point se kaise pata karoge ki ek drav pure hai ya nahi?
Drav ko garam karke thermometer se dekho. Agar woh ek tay tapmaan pe ubale aur ubalte waqt tapmaan wahi rahe, toh pure hone ki sambhavna hai. Agar tapmaan badalta rahe ya umeed se alag ho, toh usme kuch mila hai.
4. “Har uniform cheez pure hoti hai”: is baat ko galat sabit karo.
Cheeni ka ghol uniform dikhta hai, par usme cheeni aur paani do padarth hain. Paani udaane pe cheeni bach jaati hai, yaani physical tareeke se alag ho gaya. Isliye woh mixture hai, pure nahi. Toh uniform hona pure hone ka saboot nahi.
📝 Long Answer (5 marks)
1. Pure substance ki chaar pehchaan examples ke saath samjhao. Pure substance aur mixture mein teen antar likho.
Pehchaan: (1) Ek hi tarah ke kan: distilled paani mein sirf paani ke kan. (2) Fixed composition: shuddh paani mein hydrogen aur oxygen ka anupaat hamesha same. (3) Gun har jagah same: shuddh namak ka har dana ek jaisa. (4) Fixed melting/boiling point: shuddh baraf 0°C pe pighalti, shuddh paani 100°C pe ubalta (normal dabaav pe).
Antar: (i) Pure mein ek tarah ke kan, mixture mein do ya zyada. (ii) Pure ki banawat tay, mixture ki kam-zyada. (iii) Pure ko physical tareeke se alag nahi kar sakte, mixture ko kar sakte hain.
2. Matter ka vargikaran (classification) ek chart ki madad se samjhao aur har group ke do examples do.
Matter ke do bade group: pure substance aur mixture.
Pure substance ke do prakar: element (tamba, oxygen) aur compound (paani, namak).
Mixture ke do prakar: uniform (hawa, cheeni ka ghol) aur non-uniform (mitti wala paani, bhel).
Chart: Matter → [Pure substance → Element, Compound] aur [Mixture → Uniform, Non-uniform]. (Upar Diagram 2 dekho.)
📰 Case-Based Question
Priya ke papa car ki battery mein paani daalne ke liye dukaan se “distilled water” ki bottle laaye. Priya ne poocha ki ghar ka RO wala paani kyun nahi daal sakte. Papa ne bataya ki usme kuch minerals ghule hote hain. Usi din mummy ne bazaar se “pure honey” aur iodised namak kharida. Shaam ko Priya ne dekha ki chai ke bartan ke andar safed parat jami hai.
Q1. Kahani mein kaun sa paani science ki nazar mein pure substance hai, aur kyun?
Distilled water, kyunki usme sirf paani ke kan hain, koi ghuli cheez nahi.
Q2. “Pure honey” mein “pure” kis bhasha ka hai? Science ki nazar mein honey kya hai?
Roz ki (dukaan wali) bhasha ka: matlab milawat nahi. Science mein honey ek mixture hai, kyunki usme paani aur kai tarah ki sugars hain.
Q3. Iodised namak pure substance hai ya mixture? Kaaran do.
Mixture, kyunki usme namak (sodium chloride) ke saath thoda iodine wala padarth milaya gaya hai. Do padarth hain.
Q4. Chai ke bartan mein safed parat kya batati hai?
Paani mein salts ghule the. Paani baar-baar ubal kar udta raha aur salts bartan mein jam gaye. Matlab ghar ka paani mixture hai.
🚀 HOTS
1. Rohan kehta hai: “Sone ki anguthi pure hai kyunki usme sirf sona dikhta hai.” Uski baat jaancho.
Zaroori nahi. Zyada tar anguthiyan 22 carat ya usse kam ki hoti hain, jisme sone ke saath tamba ya chandi mili hoti hai. Yeh alloy (mixture) hai jo uniform dikhta hai. Sirf dekh kar purity tay nahi kar sakte; melting point jaisi jaanch chahiye.
2. Do glass mein saaf paani hai. Ek distilled hai, ek mein namak ghula hai. Bina chakhe kaise pehchanoge?
Teen tareeke: (1) Dono ki kuch boondein plate pe uda do, jahan safed nishaan bache woh namak wala. (2) Dono ko garam karke thermometer dekho; namak wala 100°C se upar ubalega. (3) Dono ko freezer mein rakho; namak wala der se jamega.
3. Priya kehti hai: “Hawa har jagah ek jaisi dikhti hai aur dikhti bhi nahi, isliye hawa pure substance hai.” Kya woh sahi hai?
Nahi. Hawa mein nitrogen, oxygen, carbon dioxide, paani ki bhaap jaisi kai gases hain, yaani kai tarah ke kan. Uski banawat bhi tay nahi: shahar ki hawa mein dhuan aur CO₂ zyada, baarish ke mausam mein nami zyada. Aur hawa ko thanda karke uski gases alag ki ja sakti hain. Isliye hawa ek uniform mixture hai, pure substance nahi.
🏆 Olympiad Corner
1. Shuddh sona 24 carat maana jaata hai. 22 carat sone mein lagbhag kitna percent sona hai?
22 ÷ 24 × 100 = lagbhag 91.67% sona. Baaki lagbhag 8.33% tamba/chandi jaise dhatu hain. Isliye 22 carat sona mixture (alloy) hai.
2. Inme se kis padarth ka boiling point fixed hoga? (a) Samudra ka paani (b) Doodh (c) Distilled paani (d) Cheeni ka ghol
✅ (c): sirf distilled paani pure hai, baaki teeno mixture hain jinke boiling point fixed nahi.
3. Ek scientist ko ek safed padarth mila. Woh theek 801°C pe pighla aur poora pighalne tak tapmaan wahi raha. Paani mein ghol kar udaane pe wahi padarth wapas mila. Yeh pure hai ya mixture?
Pure substance hone ki sambhavna bahut zyada hai, kyunki melting point tay hai aur pighalte waqt tapmaan nahi badla. (Asal mein shuddh namak, sodium chloride, lagbhag 801°C pe pighalta hai.)
📚 Aur Padho (External Reference)
- NCERT Class 8 Science Curiosity, Chapter 8 (official PDF): section “What are pure substances?” dekho
- DIKSHA: Sarkar ka free learning platform, NCERT ke videos ke liye
💖 CharuMam Motivation
Pure substance ki sabse badi khoobi kya hai? Woh kahin bhi jaaye, uski banawat nahi badalti. Shuddh paani Kashmir ka ho ya Kerala ka, andar sirf paani hi hota hai, koi milawat nahi.
Aap bhi aise hi bano, beta. Dost dekh rahe hon ya na dekh rahe hon, school ho ya ghar, aapki imaandari aur mehnat har jagah same rahe. Wahi aapki “fixed composition” hai, aur wahi aapko sabse alag aur khaas banata hai. 🌱
— CharuMam
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