ChemistryKhaga · Class 6-8
Wapas aane wala badlav, na aane wala badlav
Barf pighal ke paani ban jaati hai aur paani phir se barf ban sakta hai. Par kya pakki hui roti kabhi wapas aata ban sakti hai?
Socho pehle… phir dekho jawab
Nahi! Barf ka pighalna ek physical change hai — sirf roop badla, cheez wahi rahi. Roti ka sikna ek chemical change hai — nayi cheez ban gayi, jo wapas nahi palatti.
Physical change mein cheez ka shape, size ya state badalta hai, par andar se woh wahi rehti hai. Jaise kaagaz phaadna, barf pighalna, ya cheeni ko paani mein gholna. Aksar inhe wapas bhi laaya ja sakta hai.
Chemical change mein nayi cheez banti hai. Doodh se dahi jamna, lohe ki cycle pe jung lagna, doodh ka phatna, roti ka sikna — yeh sab chemical change hain. Nishaani: rang badalna, gandh aana, gas ya garmi nikalna.
Plaster of Paris (POP) ka safed powder paani mein milao toh thodi der mein woh garam hota hai aur sakht ho jaata hai. Yeh chemical change hai. Isiliye POP ki murti paani mein jaldi nahi ghulti, jabki kacchi mitti ki murti paani mein bikhar jaati hai.
Ghar pe try karo
Ek glass paani mein ek chammach cheeni gholo — cheeni gaayab? Ek din dhoop mein rakh do, paani udega aur cheeni ke daane dikhne lagenge (physical change). Ab mummy se poocho: dahi ko kya wapas doodh bana sakte hain? (Chemical change!)
Wow!
Tumhari cycle ki chain pe laal-bhoori jung asal mein lohe, hawa aur nami ne mil ke banayi hui ek bilkul nayi cheez hai.
3 sawaal
- Inmein se chemical change kaunsa hai?
Jawab dekho
Doodh se dahi banna. Dahi ek nayi cheez hai jo wapas doodh nahi ban sakti.
- Physical change mein kya hota hai?
Jawab dekho
Shape ya state badalta hai, cheez wahi rehti hai. Physical change mein sirf roop badalta hai, andar ki cheez same rehti hai.
- Cycle pe jung lagne ke liye lohe ke saath kya chahiye?
Jawab dekho
Hawa aur nami. Lohe ko jung lagne ke liye oxygen (hawa) aur paani/nami dono chahiye.
NCERT se jodo: NCERT Class 7 Science — physical aur chemical changes