Dhaatuon par Hawa aur Paani ka Asar

Class 7 Science · Chapter 4: Dhaatu aur Adhaatu ki Duniya · NCERT Curiosity section 4.2–4.3

Seekho

Bahar chhoda loha bhoori papdi pakadta hai. Meher teen saaf keel ek hafte jaanchti hai. A: band bottle mein silica gel ke saath (sirf sookhi hawa). B: ubale-thande paani mein upar tel (paani, hawa nahi). C: khuli bottle mein aadhi paani mein (hawa aur paani). Sirf C bhoori hoti hai.

To lohe ko hawa aur paani dono (nam hawa) chahiye bhoori parat jung (rust) banaane ko; prakriya jung lagna hai. Taambe par hari aur chaandi par kaali parat: hawa, paani aur doosre padaarthon se dhaatu ka aisa dheema nuksaan corrosion hai. Paint, tel, grease aur zinc ki parat (galvanisation) lohe ko bachaate. Jung se Bharat ka har saal bhaari nuksaan.

iron + air + water → rust

Dilli ka Lauh Stambh, Chandragupta II ke samay 1600 se zyaada saal pehle bana, lagbhag 8 m ooncha, 6000 kg se bhaari, aur mushkil se jung khaaya: prachin Bharat ke dhaatu kaushal ka pramaan.

Teacher saaf magnesium ribbon jalaati hain: chakachaundh safed lau safed powder chhodti hai, magnesium oxide. Paani mein ghulkar ye laal litmus ko neela karta hai: dhaatu ke oxide aam taur par basic. Sodium hawa aur paani se itni tez kriya karta hai ki use kerosene mein rakhte hain.

magnesium + oxygen → magnesium oxide (basic)

Explore: jung ka prayog.

1. Steps kram mein lagao.

Yaad rakho

• Loha sirf hawa aur paani dono se jung khaata; jung corrosion ka ek roop.
• Dhaatuein jalkar basic oxide; sodium kerosene mein rakha jaata.

Quick check

Kaunsi keel jung khaati: sookhi hawa mein, tel wale ubale paani mein, ya khuli bottle mein aadhi paani mein?

1. khuli bottle mein aadhi paani mein
2. sookhi hawa mein
3. tel wale ubale paani mein
4. teeno

Socho

Teen keel tel, paani aur sirke mein dubaayi. Kaunsi jung nahi khaayegi, aur kyun?

Practice

Teen levels (easy, medium, hard) ke naye sawaalon se practice karo, kuch hands-on, hints aur hal ke saath. Topic poora karne ke liye pichhle 5 mein se 4 sahi karo.