NCERT Solutions Class 7 Science Chapter 2: Exploring Substances: Acidic, Basic, and Neutral (Hinglish)

Curiosity Grade 7 (Reprint 2026-27) ke Chapter 2, Exploring Substances: Acidic, Basic, and Neutral, ke har sawaal ke jawab: Activities 2.1 se 2.7 aur unki tables, text aur boxes ke sawaal, Let Us Enhance Our Learning ke saare baarah sawaal, Dive Deeper aur projects. Page numbers kitaab ke hisaab se hain (pages 7–22). Table ki entries wo nateeje hain jinki ummeed karni chahiye; class mein apne avlokan likho. Chhote notes: Chapter 2 ke notes.

Activity 2.1: litmus (pages 8–10)

Table 2.1, ummeed ke nateeje.

• Sirka, nimbu ka ras, imli ka paani aur amla ka ras: neela litmus laal ho jaata hai; laal litmus nahi badalta.
• Baking soda ka ghol, saabun ka ghol, washing powder ka ghol aur choone ka paani: neela litmus nahi badalta; laal litmus neela ho jaata hai.
• Nal ka paani, cheeni ka ghol aur namak ka ghol: koi bhi kaagaz nahi badalta.

Table 2.2. Group A (neela litmus laal): sirka, nimbu ka ras, imli ka paani, amla ka ras. Group B (laal litmus neela): baking soda ka ghol, saabun ka ghol, washing powder ka ghol, choone ka paani. Group C (koi badlaav nahi): nal ka paani, cheeni ka ghol, namak ka ghol.

Kya aas-paas ke pedon pe lichens dikhte hain? Puraane pedon ke tane aur chattaanon pe bhoore-hare, papdi ya patti jaise dhabbe dhoondho. Ye saaf hawa aur bharpoor baarish waali jagah ugte hain, isliye inka milna achha sanket hai.

Group C ke padaarthon ki prakriti. Ye neutral hain: na acidic na basic.

Activity 2.2: khatta aur kadva (page 11)

Kya Group A ke saare padaarth khaaye jaate hain, aur unka swaad kaisa hai? Sirka, nimbu ka ras, imli ka paani aur amla ka ras sab khaaye jaate hain, aur sab khatte hain, kyunki unme acid hain.

Kuch padaarthon ke sabse aam acid. Nimbu: citric acid. Dahi: lactic acid. Imli: tartaric acid. Sirka: acetic acid.

Baking soda ka ghol ungliyon ke beech ragadne pe kaisa lagta hai? Saabun jaisa chikna, jaise basic padaarth aam taur pe hote hain.

Litmus na ho to kya doosre prakritik padaarth indicator ka kaam kar sakte hain? Haan: laal gulaab, laal gudhal, chukandar, patta gobhi aur jamun ke extract, aur haldi, sab acid ya base ke saath rang badalte hain.

Activities 2.3 aur 2.4: red rose extract (pages 12–13)

Table 2.3, ummeed ke nateeje. Sirka, nimbu ka ras, imli ka paani aur amla ka ras extract ko laal karte hain: acidic. Baking soda ka ghol, saabun ka ghol, washing powder ka ghol aur choone ka paani use hara karte hain: basic. Nal ka paani, cheeni ka ghol aur namak ka ghol use nahi badalte: neutral.

Table 2.2 se tulna. Haan, jo namoone extract ko laal karte hain wo Group A ke hain, jo hara karte hain wo Group B ke, aur jo use nahi badalte wo Group C ke. Yaani red rose extract bhi litmus ki tarah hi padaarth baantta hai.

Hydrangea: kya maali phool ka rang badal sakte hain? Haan. Mitti zyaada acidic karne se neele phool aate hain, aur zyaada basic karne se gulaabi ya laal.

Activity 2.5: haldi ka kaagaz (pages 14–15)

Table 2.4, ummeed ke nateeje. Baking soda ka ghol, saabun ka ghol, washing powder ka ghol aur choone ka paani haldi ke kaagaz ko laal karte hain. Nimbu ka ras, amla ka ras, imli ka paani, sirka, nal ka paani, cheeni ka ghol aur namak ka ghol use peela hi chhodte hain.

Kya saare namoone iska rang badalte hain? Nahi; sirf basic namoone.

Jo namoone ise nahi badalte wo Group A ke acidic aur Group C ke neutral namoone, dono hain.

Kya haldi ka kaagaz acidic padaarthon ki jaanch kar sakta hai? Nahi. Acid aur neutral, dono use peela chhodte hain, isliye ye sirf base pakad sakta hai.

Ashwin ka Guru Purnima card: sandesh kis ghol se likha ja sakta tha? Kisi bhi basic ghol se: baking soda ka ghol, saabun ka ghol, washing powder ka ghol ya choone ka paani. Jahan ye sookhe haldi ke kaagaz ko chhoota hai, kaagaz laal ho jaata hai, isliye sandesh laal dikhta hai.

Activity 2.6: gandh waala indicator (page 16)

Kya kuch padaarthon ki gandh acid ya base ke saath badalti hai? Haan; inhe olfactory indicators kehte hain.

Avlokan. Boondon se pehle dono pattiyon se pyaaz ki gandh aati hai. Boondon ke baad imli ke paani, ek acid, waali patti se ab bhi pyaaz ki gandh aati hai, par baking soda ke ghol, ek base, waali patti ki pyaaz waali gandh ud jaati hai. Sirka aur nimbu ka ras jaise doosre acid gandh rehne dete hain; saabun ka ghol aur choone ka paani jaise doosre base use uda dete hain.

Activity 2.7: neutralisation (pages 17–18)

Avlokan. Paani mein nimbu ka ras lagbhag rangheen dikhta hai. Neele litmus ghol ki ek boond ise laal karti hai, yaani ye acidic hai. Choone ka paani boond boond hilaate hue daalne pe ye kuch der laal rehta hai, phir neela ho jaata hai: ghol ab acidic nahi.

Nimbu ke ras ki ek aur boond se rang kyun badalta hai? Neutralisation ke baad ghol bas thoda sa basic hota hai, isliye acid ki ek boond use phir acidic bana deti hai, aur litmus waapas laal ho jaata hai.

Roz ki zindagi mein neutralisation (pages 18–19)

Situation 1: geele baking soda ne Keerthi ke cheenti ke kaatne mein kyun madad ki? Cheenti ne formic acid daala, jo acid hai; baking soda base hai, isliye usne acid ko neutral kar diya. Tumhare ilaake ke nuskhe: jawab alag honge. Aam nuskhe hain baking soda ka paste, aur kaate hue hisse ko saabun aur paani se dhona, kyunki saabun basic hai; kuch parivaar soojan kam karne ke liye barf lagaate hain.

Situation 2: kisaan ke liye kya ilaaj? Zyaada chemical khaad se mitti acidic ho gayi thi, isliye ilaaj hai choona daalna, jo base hai. (Mitti basic ho to khaad ya compost daalte hain; neutral ho to shaayad poshak tatv kam hain.)

Situation 3: machhliyan kyun mar rahi hain, aur kya karein? Jheel mein chhoda gaya factory ka kachra unhe nuksaan pahuncha raha ho sakta hai. Agar kachra acidic hai, to chhodne se pehle use basic padaarth se neutral karna chahiye.

Let us wrap up (page 19)

Swaagat ke shabd kyun ubhar aaye? Shabd shaayad kaagaz pe saabun ke ghol jaise basic ghol se likhkar sukhaaye gaye the. Spray haldi ka ghol tha: usne kaagaz ko peela kiya, aur jahan base mila wahan laal kar diya, isliye shabd dikhne lage. Haan, haldi ka spray aur saabun ki likhaai ek sambhaavna hai.

Let Us Enhance Our Learning (pages 20–21)

1. (iii) Sirka. Ghol basic hai; sirf acid, zyaada maatra mein, use neutral karke litmus ko waapas laal kar sakta hai. Choone ka paani aur baking soda base hain, aur namak ka ghol neutral hai.

2. (iv) Basic, basic aur basic. Laal litmus ka neela hona, haldi ka laal hona aur red rose extract ka hara hona, teeno base dikhaate hain.

3. Fig. 2.13: patti ka sira hara ho jaata hai, isliye ghol basic hai. Fig. 2.14: patti nahi badalti, isliye neutral. Fig. 2.15: sira gehra laal ho jaata hai, isliye acidic.

4. Dravya acidic hai. Neela litmus laal hua, jo sirf acid se hota hai. Laal litmus nahi badla, isliye ye basic nahi, aur haldi nahi badli, jo theek baithta hai, kyunki haldi sirf base se badalti hai.

5. Olfactory indicator, jaise kati pyaaz ke saath rakhi kapde ki pattiyan. Aankhon pe patti hone se Manya rang ka badlaav nahi dekh sakti, par soongh sakti hai: acidic ghol mein pyaaz ki gandh rehti hai aur basic mein ud jaati hai. (Extra: vanilla essence aur laung ka tel bhi base mein apni gandh kho dete hain.)

6. Ek dravya se likho, sookhne do, phir indicator spray karo:

• Saabun ya baking soda ka ghol, us pe haldi ka ghol spray: peele pe laal likhaai.
• Baking soda ka ghol, us pe red rose extract: hari likhaai.
• Nimbu ya santare ka ras, us pe red rose extract: laal likhaai.
• Sirka, us pe neela litmus ghol: laal likhaai.
• Nimbu ka ras, us pe haldi ka ghol: likhaai chhupi rehti hai, kyunki haldi acid se nahi badalti.

7. Angoor ka ras acidic hai, isliye extract laal hua. Baking soda base hai: pehle ye acid ko neutral karta hai, aur jab kaafi daalne pe mishran basic ho jaata hai, rang hara ho jaata hai. (Extra: bulbule bhi dikh sakte hain, kyunki baking soda acid se kriya karta hai.)

8. Santare ka ras acidic hai, isliye aisa indicator use karo jo acid ke saath badle: red rose extract spray karo (shabd laal ho jaayenge) ya neela litmus ghol lagaao (shabd laal ho jaayenge). Haldi kaam nahi karegi, kyunki wo acid ke saath nahi badalti.

9. Prakritik indicator paudhon ke rangeen hisson se bante hain. Udaaharan, red rose extract: laal gulaab ki giri pankhudiyan ikattha karo, dhokar kuchlo, garam paani se dhako (bade ke saath), 5 se 10 minute ruko aur chhaano; rangeen dravya indicator hai. Haldi ka kaagaz doosra udaaharan hai: filter paper ko haldi ke paste mein dubaao, sukhaao aur pattiyon mein kaato.

10. Haan. Har ek ki ek boond haldi ke kaagaz pe daalo: jo use laal kare wo baking soda ka ghol hai. Sirka aur cheeni ka ghol dono use peela chhodte hain, isliye akeli haldi unhe alag nahi kar sakti. Ab baking soda ke ghol se ek laal dhabba banao aur baaki dono ki kuch boondein daalo: jo laal dhabbe ko phir peela kar de wo sirka hai, ek acid jo base ko neutral karta hai; jo use laal rehne de wo cheeni ka ghol hai, jo neutral hai.

11. Dravya X basic hai, kyunki red rose extract base mein hara hota hai. Amla ka ras acidic hai, isliye daalne pe pehle wo base ko neutral karta hai, aur zyaada amla ras se mishran acidic ho jaata hai aur extract laal ho jaata hai.

12. Mitti acidic ya basic ho sakti hai. Jaanchne ke liye mitti ko paani mein milaao, baithne do ya chhaano, aur paani ko litmus paper se jaancho (red rose extract bhi chalega). Acidic mitti ka ilaaj choone se ho sakta hai; basic mitti ka ilaaj khaad ya compost jaise organic padaarth se.

Dive Deeper (page 22)

Sirke se ande ke chhilke ya marble pe bulbule kyun bane, par saabun ke ghol se nahi? Sirka acidic hai, aur ande ka chhilka aur marble acid se kriya karke ek gas chhodte hain jo bulbule banaati hai. Saabun ka ghol basic hai, isliye aisi koi kriya nahi hoti. Extra: ande ka chhilka aur marble calcium carbonate ke bane hote hain, aur gas carbon dioxide hai.

Disciplinary Exploratory Projects (page 22)

• Indicators se rangoli: haldi powder se rangoli banao aur saabun waala paani chhidakkar laal design banao, ya red rose extract se rang bharo aur use nimbu ke ras (laal) aur baking soda ke ghol (hara) se chhuo.
• Alag alag srot ka paani: baarish, nal aur nadi ya kuen ke paani ko litmus ya red rose extract se jaancho aur tulna karo. Zyaadatar nal ka paani neutral ke kareeb hota hai; doosre srot alag ho sakte hain. Kyun, is pe charcha karo.
• Apni mitti: mitti ko paani mein milaao, baithne do, aur paani ko litmus ya red rose extract se jaancho ki wo acidic, basic ya neutral hai.