Rust is usually used to refer to a very common, reddish-brown compound called iron oxide (Fe2O3). Iron oxide is formed when iron and oxygen react in the presence of water or moisture in the air. Rust occurs when iron or its alloys, such as steel, corrode.
The process of rusting is a combustion reaction, similar to fire. Left in contact with oxygen, iron will react with the oxygen to form rust.
There are certain factors that can speed up the rusting process. For
example, water speeds up the reaction. Other substances, such as salt,
can also increase the speed of the rusting process.
This experiment will help you to find out what caused rust to occur:
MATERIALS:
5 glasses (transparent), steel wool, water, salt, bicarbonate of soda and vinegar.
PROCEDURE:
- Line up the glasses and label each one as 1, 2, 3, 4 and 5, so that you can write down what you have put in each.
- Put a bit of steel wool in each container.
- Pour some water into your first glass labelled '1' and put the lid on it.
- Leave your second glass labelled '2' open and exposed to the air (air contains water vapour).
- Mix some salt with some tap water and pour this into your third glass labelled '3' and place the lid on it.
- Add a pinch of bicarbonate of soda in your fourth container labelled '4' and place the lid on it. (bicarbonate of soda may help to remove water vapour from the trapped air).
- Pour some vinegar into your fifth glass labelled '5' and put the lid on it.
Clue: Container '4' will only start to show rust if the air and any water vapours get through the lid into the glass.