May, 2016:
Kids, back in 2010, we looked at the reaction of iron in steel wool with oxygen by combining the wool with vinegar to remove the protective coating on it and saw the temperature rise as the wool is wrapped around a thermometer - http://chicagoacs.org/articles/212. The temperature went up because of the reaction of the steel wool with the atmospheric oxygen.
Now that camping season is upon us, we can take advantage of this very hot reaction to help us make our campfire. You know that when starting a campfire, it is often best to have some very small twigs or dried leaves to get the fire started because logs don’t catch fire easily. We’ll take advantage of the very fine steel wool for the same reason – the small twigs and the steel wool both have a lot of surface area for the reaction to take place.
Please note: All chemicals and experiments involve an element of risk, and no experiments should be performed without proper adult supervision.
Materials:
- Very fine steel wool (grade 000 or 0000)
- A 9V battery
- An aluminum pan
Make sure that an adult is present anytime fire is involved.
Try this:
- Pull a piece of steel wool off from the pad and pull it apart so that it is not a compact ball.
- Touch the leads of the 9V battery to the steel wool and remove the battery from the wool.
Did you see the sparks in the wool? If you’re looking to start a campfire you will want some tinder nearby to get the fire started. Blowing on the sparks will allow them to travel through the wool more completely.
By touching the leads of the battery to the wool, you complete the circuit of the battery. Electricity will begin to flow through the wire (just like in an incandescent light bulb). As electrons flow, friction is created and the fine wire heats up and the iron is able to react with the oxygen in the atmosphere. Blowing on it keeps oxygen coming to the wire for the reaction to continue. Larger iron blocks will not catch fire because the iron does not have enough oxygen around it and the iron cannot get hot enough because the heat can too easily disperse to deep inside the block of iron. There is not enough surface area in the block of iron.
The wool may also have a bit of an oil residue on it and that oil will also combust. The reaction that is occurring is:
4 Fe + 3 O2 -> 2 Fe2O3
Although it may not seem like it, the mass of the combusted wool should be significantly more than the mass of the initial wool because it has added to it the mass of the oxygen from the atmosphere.
To view all past “ChemShorts for Kids”, go to: http://chicagoacs.org/articles.php?article_category=1
