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  • 2/9/2013

Iron Burns …Slowly

iron burns slowly

Sometimes a big load of iron in a ship can get hot. The heat can even set other materials on fire.

That's because the iron is rusting, which means it is burning very, very slowly. Iron rusts in a chemical reaction called oxidation. That means the iron reacts with oxygen gas from the air. Oxidation is the chemical reaction that occurs when anything burns in air.

Like most oxidations, rusting gives off heat. But rusting is a slow process that gives off very little heat. It becomes a fire hazard only when a lot of iron is allowed to rust in a closed-up space.

You can do a safe experiment to see the effect of this reaction.

Put a pad of steel (iron) wool into a jar. Pour in some water to wet the steel wool, then pour out water till only a little is left. Water helps the reaction go faster. Now stretch a balloon loosely across the mouth of the jar. (I cut off the neck of a balloon and threw away the neck. Then I used a rubber band to fasten the balloon over the mouth of the jar.)

Leave the jar where you can watch it. In a few hours the balloon will begin to bend inward. By the next morning, it will be sucked into the jar. Orange-red rust will be collecting on the steel wool and falling off to the bottom of the jar.

The sucking-in of the balloon shows you that some part of the air was used up to make the rust. Our experiment does not prove that the gas used up was oxygen. But actually, there is no other gas in the air that will react with iron.

I thought that my jar of rusting steel wool did warm up just a little--certainly not enough to be dangerous. But you can see how a room full of rusting steel wool might get very warm. Let's not try that.

Source: highlightskids.com


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