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Procedure

1. Wet a measuring cylinder and sprinkle some iron fillings on the wet surface.2. Remove the excess iron fillings.3. Invert the measuring cylinder in a trough of water.4. Read the air column in the measuring cylinder.5. Leave the set up for 48 hours.6. Read and record the volume of the air column. Record all your observations.

Discussion

The measuring cylinder is made wet to ensure that the iron fillings to stick on to the wet surface. When iron fillings are left for 48 hours in the measuring cylinder, a brown coating is formed. The brown coating is rust. Rust is a compound of iron and oxygen. During rusting oxygen is used and therefore water rises up in the measuring cylinder to replace the volume of air used during rusting. About 20% of air by volume is used up during rusting.