Malleability, Ductility aur Sonority

Class 7 Science · Chapter 4: Dhaatu aur Adhaatu ki Duniya · NCERT Curiosity section 4.1.1–4.1.3

Seekho

Zoya aur Kabir gaon ke lohaar ke paas jaate hain. Wo lohe ke gutke ko laal garam karke hathaude se peetkar kulhaadi banaata hai. Tawa, baalti, chimta, phawda aur khurpi sab lohe se bante hain. "Kya doosre padaarth bhi peetkar chapte ho sakte hain?" Zoya sochti hai.

Taamba, aluminium aur loha chamakdaar aur sakht: ye dhaatu hain. Koyla, gandhak aur lakdi feeke. Peetne par dhaatuein chapti hoti hain: patli chaadar mein peetne ka gun malleability hai. Mithaai ka chaandi vark aur aluminium foil udaharan; sona aur chaandi sabse malleable. Koyla aur gandhak toot'te hain: ye bhangur hain. Lakdi dono nahi.

Saari dhaatuein sakht nahi: sodium aur potassium chaaku se katte hain, aur paara kamre ke taapmaan par tarl. Dhaatuon ko taar mein bhi kheencha ja sakta hai: ye ductility hai. Taambe-aluminium ke taar, sitar-guitar ke taar, crane aur pul ki steel rassiyan sab isi se. Ek gram sone se lagbhag 2 km lamba taar!

Steel ka chammach ya sikka giraao to khanakta hai; koyla ya lakdi giraao to dheemi aawaaz. Dhaatuon ka khanakne ka gun sonority hai: school ki ghanti, mandir ki ghanti aur ghungroo socho. Jo dekh nahi sakta wo chhadi thapthapaakar aawaaz se dhaatu aur lakdi pehchaan sakta hai. Hal jaise lohe ke auzaaron ne Bharatiya sabhyata ko badhaaya, taambe aur sone ke bahut baad.

Explore: hathauda test.

1. Har cheez par hathauda maarkar sort karo.

Yaad rakho

• Dhaatuein chamakdaar, malleable (chaadar), ductile (taar) aur sonorous (khanak).
• Koyla aur gandhak bhangur; paara tarl dhaatu; sodium naram.

Quick check

Kaunsa gun aluminium ko foil banne deta hai?

1. malleability
2. ductility
3. sonority
4. brittleness

Socho

Kyun maana jaata hai ki log taamba lohe se pehle use karte the?

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.