A simple experiment involving rust...

Let's take a look at the common, everyday occurance of rust. We see rust, that reddish-brown flaky stuff, on the sides of old cars, or on our bicycle that we absent-mindedly left outside for an entire winter. But what is rust caused by? You can try this simple experiment at home to find out.

What you need:

Two pieces of steel wool

Two pie pans

Two glass cups or beakers

Some water

Two pieces of clay or putty

What you do:

Fill the pie pan with water until it is half full. Stick the putty to one side of the steel wool, and attach the steel wool to the bottom of the glass. Place the glass, upside down, into the pie pan. Leave this to sit overnight and observe any changes during the next few days. Repeat the same procedure with the second set of materials, only this time, fill the pie pan with more water. Let the second set sit overnight as well.

What's going on here?

If all goes right, the water should begin to rise up into the glass and the steel wool should start to rust. Why does this happen? Well, rust forms as the steel, which is mainly composed of iron, reacts with the oxygen in the air. But if I left a piece of steel wool on the countertop overnight, it would not rust. The key is that we are suspending the iron over water. Inside the tube, there are the correct elements for rust: iron, oxygen in the air, and water vapor. How do I know that there is water vapor in the glass? Any time we have liquid water, a certain amount of that liquid spontaneously turns to gas even if we didn't heat it! The oxygen combines with regular iron to turn it into iron(III) oxide. Iron (III) oxide, Fe₂ O₃, is commonly known as rust.