The Rusty Nail Experiment
Observe iron reacting with oxygen and water.
What this lesson covers
Why it matters
Leave an iron nail in moist air and watch it slowly turn reddish-brown and flaky as rust forms. This is not just dirt; it is a brand-new substance born from air and water.
The idea in plain words
Watch the slow change: iron, oxygen and water together form the flaky reddish-brown solid we call rust.
Predict first
You leave a bright iron nail in damp air for a week. What will you most likely see?
In moist air iron reacts slowly with oxygen and water to form hydrated iron(III) oxide — the flaky reddish-brown solid we call rust.
- Iron melts into a liquid pool
- A flaky reddish-brown coat of rust forms — correct
- Iron disappears completely
- A shiny black layer forms instantly
What you do
Leave the iron nail in moist air. Slowly, oxygen and water attack the iron and a flaky reddish-brown coat of rust (hydrated iron(III) oxide) creeps over its surface.
Check yourself
What is the reddish-brown, flaky solid that forms on the nail?
In moist air iron reacts with oxygen and water to form hydrated iron(III) oxide — the flaky reddish-brown solid called rust.
Which TWO things from the surroundings does iron need in order to rust?
Rusting needs BOTH oxygen and water. Dry oxygen alone, or water with no air, will not rust iron.
Why does an oiled or painted iron gate resist rusting?
A coat of paint or oil keeps air and moisture away from the iron surface, so rusting is stopped.
- Rust — hydrated iron(III) oxide (Fe₂O₃·xH₂O) — correct
- Black magnetite (Fe₃O₄)
- Pure shiny iron (Fe)
- Iron sulphide (FeS)
- Oxygen and water (moisture) together — correct
- Oxygen only
- Water only
- Heat and bright light
- The coat keeps air and moisture away from the iron — correct
- Oil makes the iron too heavy to react
- Paint turns the iron into gold
- It cools the iron down