Maya reluctantly opened to . She found the exact question: “Q. 4(c) – Explain with an example why the mass increases in some chemical changes.”
The topic? Physical and Chemical Changes — specifically, why a rusted nail weighed more than a new one. Her textbook said: “Rusting is oxidation. Iron combines with oxygen to form iron oxide.” But in her head, that made no sense. If something rusts and flakes away, shouldn’t it weigh less ? viraf j dalal chemistry class 8 icse solutions
Instead of just copying the answer, she read the carefully: Solution hint: In rusting, iron (Fe) from the nail combines with oxygen (O₂) from the air and water vapor to form hydrated iron(III) oxide (Fe₂O₃·xH₂O). The rust includes the original iron plus the added oxygen. Therefore, the total mass of the rusted nail is greater than the original nail. Then, Viraf J. Dalal’s book had a "Try This" box: Perform an activity – weigh a clean iron nail, leave it in moist cotton for 3 days, weigh again. Maya reluctantly opened to