Rust and Moisture
To find out if the phenomenon of rusting is dependant on the presence of moisture
Theory & Background
Did you know that air around us has incredible properties? Rust is formed by the ‘oxidation’ of iron in the presence of moisture. A desiccator is a special container that has two ‘layers’ separated by a wire gauze; this allows different substances to be placed in it without mixing the two while still allowing them to ‘interact’ since they are both equally exposed to the air that circulates within this container. Calcium chloride crystals are used to absorb any moisture present in air.
Required Materials
- Desiccator
- Iron nails
- Calcium Chloride crystals
Estimated Time
Less than 10 minutes to set up the apparatus and approximately 1 week to make the observations
Step-By-Step Procedure
Prepare the desiccator by placing a few clean, dry iron nails above the wire gauze of a desiccator.
Place Calcium Chloride crystals in the lower layer / base of the desiccator.
Control – Tie a few more nails, dip it in water and hang it on the outside of the desiccator.
Leave the set-up untouched for a few days and observe.
Experiment Tips
- Do exercise caution while handling rust; special care must be taken to ensure that it does not come in direct contact with open wounds or ruptured skin so as to avoid an infection.
- In case a desiccator is not available, you may substitute it with two test tubes – one with iron nails placed in it, followed by a layer of cotton wool, Calcium Chloride crystals and cotton wool again; the other test tube (control) can simply have some moistened iron nails placed in it, exposed to air.
Observation
The control (nails hung outside the desiccator) which was exposed to both air and moisture are found to rust, while those inside the desiccator remain bright and rust-free.
Result & Conclusion
The calcium chloride crystals absorbed all the moisture in the desiccator and this prevented the iron nails inside the desiccator from rusting. The control set-up however, allowed rust to form since it was exposed to moisture in the air. Hence it is obvious that iron does not oxidize or rust in the absence of moisture.