Class 8 Science · Chapter 9
Short answer:
Chapter 9 — The Amazing World of Solutes, Solvents, and Solutions ek nazar me: Solute (kam quantity, dissolve hone wala) + Solvent (zyada quantity, dissolve karne wala) = Solution. Saturated solution me aur solute dissolve nahi hota, unsaturated me hota hai. Concentration = Mass of solute ÷ Mass of solution × 100. Solubility temperature, nature of substance, aur pressure par depend karti hai. Suspension (settle hota hai) vs colloid (Tyndall effect, settle nahi hota) — dono true solution se different hain.
Chapter 9 poore solutions and mixtures ke concept ki neev hai — Class 8 se lekar Class 10 tak jitne bhi numericals concentration, solubility, aur saturation par aate hain, unka base yahin banta hai. Roz ke observations jaise chai me chini ghulna, cold drink me CO2 ki fizz, ya samudra ka khara paani — sab is chapter ke concepts se explain hote hain.
Is spec me hum solute solvents and solutions class 8 examples ke saath-saath saturated/unsaturated solutions, solubility ko affect karne wale factors, concentration ke numericals, aur suspension-colloid ka difference — sab CBSE marking-scheme style me cover karenge, taaki exam me full marks aayein.
Chapter 9 Summary — 5 Minute Revision
Is chapter me humne dekha ki solute + solvent = solution ka basic formula kaise kaam karta hai, aur roz ke examples (chini-paani, namak-paani, cold drink) se ise samjha. Saturated aur unsaturated solutions ka concept temperature ke saath directly juda hai — jo numericals aage Class 9-10 me concentration aur molarity ke roop me expand hote hain, unki neev yahin bantee hai.
Humne concentration ka mass percentage formula step-by-step numericals ke saath solve kiya, solubility ko affect karne wale factors (temperature, nature of solute-solvent, pressure) discuss kiye, aur suspension vs colloid vs true solution ka clear difference table-style samjha. 6 common mistakes aur 6 practice questions is topic ko exam-ready banane ke liye diye gaye hain — practice karte waqt formula pehle likho, phir values substitute karo, taaki step-wise marking me full marks milein.
In-Text Questions — Solutions
Ek glass paani me namak dalne par woh gayab kyun ho jaata hai?
Namak (solute) ke particles paani (solvent) ke particles ke beech ke gaps me evenly distribute ho jaate hain — ye process dissolution kehlata hai. Particles itne chhote ho jaate hain ki naked eye se dikhte nahi, isliye lagta hai namak "gayab" ho gaya, lekin actually woh solution me uniformly present hota hai — taste karne par pata chalta hai.
Cold drink kholte hi "fizz" kyun aati hai?
Cold drink me carbon dioxide gas high pressure par dissolve karke sealed ki jaati hai. Jaise hi bottle kholte hain, pressure achanak kam ho jaata hai, aur chunki gas ki solubility pressure kam hone par ghat jaati hai, extra CO2 gas bubbles ke form me bahar nikalne lagti hai — yehi "fizz" hai.
Chai me chini garam paani me jaldi kyun ghulti hai lekin thande paani me slow?
Kyunki temperature badhne se solvent (paani) ke particles ki kinetic energy badh jaati hai, jisse woh zyada tezi se move karte hain aur solute (chini) ke particles ke beech aasani se jagah bana lete hain. Isi liye zyadatar solids ki solubility temperature ke saath badhti hai.
Exercise Questions — Solutions (Q1–Q6)
Q1. Solute aur solvent me farak batao, ek-ek example ke saath.
Solute woh substance hai jo chhoti quantity me hota hai aur dissolve hota hai — jaise chini (sugar).
Solvent woh substance hai jo zyada quantity me hota hai aur solute ko dissolve karta hai — jaise paani (water).
Example: chini + paani = sugar solution, jisme chini solute hai aur paani solvent hai.
Q2. Saturated aur unsaturated solution me antar spasht karo.
Ek diye gaye temperature par jab solvent me aur solute dissolve nahi ho sakta (extra solute neeche baith jaata hai / undissolved reh jaata hai), toh usse saturated solution kehte hain.
Jab solvent me abhi bhi aur solute dissolve karne ki capacity bachi ho, toh usse unsaturated solution kehte hain.
Example: 100 mL paani me agar 36 g namak hi dissolve ho sakta hai (25°C par) aur humne exactly utna hi dala hai — solution saturated hai. Agar sirf 20 g dala hai toh solution unsaturated hai.
Q3. Concentration ki definition do aur uska formula likho.
Concentration ye batati hai ki ek diye gaye solvent (ya solution) ki quantity me kitna solute dissolved hai.
Concentration = Mass of solute (g) / Volume of solution (mL ya L)
Ya phir mass percentage ke roop me:
Mass % of solute = (Mass of solute / Mass of solution) × 100
Q4. Solubility ko affect karne wale teen factors likho.
1. Temperature — zyadatar solids ki solubility temperature badhne se badhti hai (par gases ki ghat jaati hai).
2. Nature of solute aur solvent — "like dissolves like" rule — polar solute polar solvent me aur non-polar solute non-polar solvent me zyada achhe se dissolve hota hai.
3. Pressure (khaaskar gases ke liye) — pressure badhne se gas ki solubility liquid me badh jaati hai (jaise cold drink me CO2).
Q5. Ek numerical: 250 g paani me 25 g namak dissolve kiya gaya hai. Solution ka mass percentage concentration nikaalo.
Given:
Mass of solute (namak) = 25 g
Mass of solvent (paani) = 250 g
Mass of solution = 25 + 250 = 275 g
Mass % = (Mass of solute / Mass of solution) × 100
Mass % = (25 / 275) × 100 = 9.09%
Answer: Solution ki concentration approx 9.09% hai. Formula likhna, values substitute karna, aur final answer unit ke saath dena — teeno steps dikhana zaroori hai.
Q6. Suspension aur colloid me kya difference hai? Ek-ek example do.
Suspension: particles bade hote hain (naked eye se dikhte hain), light ko scatter karte hain, settle down ho jaate hain, filter kiye ja sakte hain. Example: mitti aur paani (muddy water).
Colloid: particles suspension se chhote lekin true solution se bade hote hain, settle nahi hote, Tyndall effect dikhate hain (light scatter karte hain but visible rehta hai beam). Example: doodh (milk).
Important Equations — Ek Nazar Me
| Concept | Formula / Rule |
|---|---|
| Mass percentage concentration | Mass % = (Mass of solute / Mass of solution) × 100 |
| Mass of solution | Mass of solution = Mass of solute + Mass of solvent |
| Concentration (general) | Concentration = Mass of solute / Volume of solution |
| Solubility | Solubility = (Mass of solute dissolved to saturate 100 g solvent) at given temperature |
| "Like dissolves like" rule | Polar solute → Polar solvent; Non-polar solute → Non-polar solvent |
↔ Table ko side me swipe karein
Common Mistakes — Yahan Marks Kat te Hain
- Solute aur solvent ko ulta samajhna — hamesha yaad rakho jo kam quantity me hai woh solute hai, chahe woh liquid hi kyun na ho (jaise alcohol thodi si paani me mila di jaaye).
- Saturated solution ka matlab "solution poora bhar gaya" samajhna, jabki actually iska matlab hai ek diye gaye temperature par further solute dissolve nahi ho sakta — temperature badhने par wahi solution unsaturated ban sakta hai.
- Concentration ke numericals me 'mass of solution' ki jagah galti se 'mass of solvent' se divide kar dena — formula me hamesha total solution ka mass use karo, sirf solvent ka nahi.
- Gases ki solubility ko solids jaisa treat karna — yaad rakho gases ki solubility temperature badhne par GHATTI hai, badhti nahi (isiliye garam cold drink flat ho jaati hai).
- Suspension aur colloid ko same samajh lena — suspension ke particles settle ho jaate hain aur filter ho sakte hain, colloid ke particles settle nahi hote aur Tyndall effect dikhate hain.
- Units ka dhyan na rakhna — mass percentage nikalte waqt agar solute grams me hai aur solution kilograms me diya hai, pehle same unit me convert karo, warna answer galat aayega.
Board-Style Important Questions
- Define solute and solvent with one example each.
- Numerical: Calculate the mass percentage of a solution prepared by dissolving 20 g of sugar in 180 g of water.
- Differentiate between saturated and unsaturated solutions.
- Explain why the solubility of gases decreases with increase in temperature, giving a real-life example.
- Distinguish between a solution, a suspension, and a colloid with one example of each.
- State any two factors affecting the solubility of a solid in a liquid.
Aksar Poochhe Jaane Wale Sawaal
Class 8 Science Curiosity chapter me solutes, solvents aur solutions ka topic kaunse chapter me aata hai?
Naye rationalised NCERT Class 8 Science Curiosity textbook (2026-27 session) me matter ki particulate nature, mixtures, aur solutions se related concepts alag-alag chapters me cover hote hain — jaise "Particulate Nature of Matter" aur "Nature of Matter: Elements, Compounds and Mixtures". Solutions ka topic in dono chapters se connected hai, isliye exam prep karte waqt in dono ko saath revise karo.
Solute aur solvent yaad rakhne ka aasan tarika kya hai?
Simple trick: "Solute Sota hai, Solvent Sambhalta hai" — jo kam quantity me hai aur dissolve ho raha hai woh solute, aur jo zyada quantity me hai aur dusre ko dissolve kar raha hai woh solvent. Chini-paani wale example me chini solute aur paani solvent — hamesha yehi pattern follow hota hai.
Kya paani hamesha solvent hi hota hai?
Nahi, paani ko universal solvent isliye kaha jata hai kyunki woh bohot saari substances ko dissolve kar sakta hai, lekin har situation me paani hi solvent nahi hota. Jaise alcohol-water mixture me agar alcohol zyada quantity me hai, toh alcohol solvent ban jaata hai aur paani solute.
Solubility curve kya hota hai aur ye exam me kaise use hota hai?
Solubility curve ek graph hai jisme temperature (x-axis) vs solubility (y-axis, g per 100g solvent) plot kiya jaata hai. Exam me isse pucha jaata hai ki kisi diye gaye temperature par kitna solute dissolve hoga, ya kitna extra solute crystallize ho jayega jab solution ko thanda kiya jaaye — is type ke numericals class 8 se class 10 tak repeat hote hain.
Class 8 Science Curiosity book pdf download kahan se karein 2026-27 session ke liye?
Official aur sabse reliable tarika hai NCERT ki official website ncert.nic.in ya epathshala se free PDF download karna. Third-party sites se avoid karo kyunki content outdated ya galat ho sakta hai — especially jab syllabus rationalise ho chuka hai.
Exam me solutions ke short answer questions ka best tarika kya hai answer likhne ka?
Step-wise likhne ka approach follow karo: pehle definition ek line me, phir example do, aur agar numerical hai toh formula likho, values substitute karo, final answer unit ke saath do. Har step alag se likhne se partial marks milne ke chances badh jaate hain, chahe final answer galat bhi ho jaaye.
Class 8 Science — Saare Chapters
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