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Rusting of Iron

Class 10 · CBSE Corrosion
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Mr Chemcoach-Digital Lab | NEO-LAB 7.0 · Rusting of Iron
Class 10 · CBSE · Chemical Reactions & Equations
LIVE SIM
O2 + H2O Required
Corrosion of Iron
Visual + Sound
Rusting Visualizer
Adjust environment → Watch iron corrode in real-time
Iron Nail (Fe) Environment Chamber
Water / Moisture
LOW
Air / Oxygen
LOW
Salt / Electrolytes
NONE
Time Exposed
0 days
Rust Level 0%
Iron surface is shiny · No rust yet. SAFE METAL
Control Console
4Fe + 3O2 + xH2O → 2Fe2O3·xH2O
Word equation: Iron + Oxygen + Water → Hydrated iron(III) oxide (Rust)
Water / Moisture LOW
CBSE: Moisture is essential for rusting. Dry iron does not rust.
Air / Oxygen LOW
Iron needs oxygen from air for rusting to happen.
Salt / Electrolyte NONE
Rusting is faster in salt water (coastal areas).
Time Progress 0 days
Time controls how far the rusting reaction has gone.
Quick CBSE Scenarios

What this experiment shows

Rust is hydrated iron(III) oxide, and it needs two things to form: oxygen and water. Take either away and iron does not rust, which is why the classic experiment uses three boiling tubes - one with both, one with dry air only, one with boiled water under oil. Salt does not cause rusting, but it speeds it up considerably, which is why cars rust faster near the coast and on gritted roads.

4Fe + 3O2 + 2xH2O → 2Fe2O3·xH2O

What you need

  • Four clean iron nails, degreased
  • Four boiling tubes with bungs
  • Anhydrous calcium chloride, to dry the air in one tube
  • Water that has been boiled and cooled, and a layer of oil to keep air out
  • Salt solution for the fourth tube

How it is done

  1. Tube 1: nail in ordinary tap water, open to the air - the control.
  2. Tube 2: nail with dry air only, over anhydrous calcium chloride, stoppered.
  3. Tube 3: nail in boiled water covered with a layer of oil, so no air can dissolve.
  4. Tube 4: nail in salt solution, open to the air.
  5. Leave all four for a week in the same place and compare.

What you should see

  • Tube 1 rusts. Tube 4 rusts fastest.
  • Tubes 2 and 3 stay clean - one has no water, the other no oxygen.
  • Rust is orange-brown, flaky, and does not stick, so fresh metal keeps being exposed.

Where marks are lost

  • Saying salt is needed for rusting. It only speeds it up.
  • Forgetting to boil the water in tube 3, so dissolved oxygen is still present.
  • Calling rust iron oxide with no mention of water. It is hydrated iron(III) oxide.
  • Comparing tubes kept in different places or at different temperatures.

Questions students ask

Why boil the water?
Boiling drives out dissolved oxygen. The oil layer then stops more from dissolving back in, so that tube tests water without oxygen.
Why does salt speed rusting up?
Salt water conducts much better than pure water, and rusting is an electrochemical process, so the ions let it run faster.
How is rusting prevented?
By keeping oxygen and water off the iron - paint, oil, grease or plastic - or by sacrificial protection with a more reactive metal such as zinc.

Try these next

Written for Cambridge IGCSE Chemistry 0620 and CBSE Class 9-12 by Ajay Shekhawat, founder of MrChemCoach. Run the simulator above, then check yourself against the questions.