What makes iron rust
Air and water together.
Three nails
Three iron nails are kept in three places. One has air and water. One has air but no water. One has water but no air.
Which nails will rust?
What this lesson covers
The idea
Both air and water are necessary for iron to rust.
Three nails
Three iron nails are kept in three places. One has air and water. One has air but no water. One has water but no air.
Which nails will rust?
- Only the nail with both air and water
- All three
- Only the nail in water
Three places
Open every tab. These are pictures of a lab test.
Both are needed
Iron needs both air and water to rust. Take away one of them and the iron does not rust. This also tells us how to protect iron: keep air or water away from it.
Both air and water are necessary for iron to rust.
Notes
Both air and water are necessary for iron to rust.
Check yourself
What is needed for iron to rust?
An iron nail is kept in dry air, with no water. It will ...
An iron nail is kept in water that has no air in it. It will ...
The brown flaky coating on iron is formed in ...
- Air alone. Both are necessary; air alone is not enough.
- Both air and water — correct. Yes!
- Water alone. Both are necessary; water alone is not enough.
- rust, because air is present. Both air and water are necessary, and water is missing.
- rust faster than with water. Both air and water are necessary, and water is missing.
- not rust — correct. Yes!
- not rust — correct. Yes!
- rust, because water is present. Both air and water are necessary, and air is missing.
- turn black like silver. Silver blackens in air with sulphur; iron's coating is brown rust, and here it does not form.
- dry air. Dry air has no water, and water is necessary for rust.
- moist air — correct. Yes!
- a vacuum. Rusting needs air and water.