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.
10 examples
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.