Class 7SciencePhysical and Chemical Changes

Rusting and Crystallisation

Rusting: iron reacts with oxygen and water to form rust (Fe₂O₃·xH₂O). Chemical change — reddish-brown, flaky. Prevents with painting, oiling, galvanising (zinc coating). Crystallisation: growing crystals from supersaturated solution — example copper sulphate crystals (blue). This is physical change — can dissolve crystals and get solution back.

How to study this topic

Read the core explanation once without solving.
Open the formula links below and connect them with the topic meaning.
Practice the 10 example pages one by one.
Use the AI ask page for text, voice or image-based doubts.

10 example pages

Concept check 1

For Class 7 Science, explain or solve a rusting and crystallisation question from the chapter "Physical and Chemical Changes". Focus on concept check and show the working clearly.

Definition to application 2

For Class 7 Science, explain or solve a rusting and crystallisation question from the chapter "Physical and Chemical Changes". Focus on definition to application and show the working clearly.

Formula warm-up 3

For Class 7 Science, explain or solve a rusting and crystallisation question from the chapter "Physical and Chemical Changes". Focus on formula warm-up and show the working clearly.

Reasoning practice 4

For Class 7 Science, explain or solve a rusting and crystallisation question from the chapter "Physical and Chemical Changes". Focus on reasoning practice and show the working clearly.

Board-style short answer 5

For Class 7 Science, explain or solve a rusting and crystallisation question from the chapter "Physical and Chemical Changes". Focus on board-style short answer and show the working clearly.

Mistake correction 6

For Class 7 Science, explain or solve a rusting and crystallisation question from the chapter "Physical and Chemical Changes". Focus on mistake correction and show the working clearly.

Visual interpretation 7

For Class 7 Science, explain or solve a rusting and crystallisation question from the chapter "Physical and Chemical Changes". Focus on visual interpretation and show the working clearly.

Applied word problem 8

For Class 7 Science, explain or solve a rusting and crystallisation question from the chapter "Physical and Chemical Changes". Focus on applied word problem and show the working clearly.

Revision challenge 9

For Class 7 Science, explain or solve a rusting and crystallisation question from the chapter "Physical and Chemical Changes". Focus on revision challenge and show the working clearly.

Exam recap 10

For Class 7 Science, explain or solve a rusting and crystallisation question from the chapter "Physical and Chemical Changes". Focus on exam recap and show the working clearly.