Kids, what kind of chemical reaction makes heat? Exothermic chemical reactions produce heat. In this reaction vinegar is used to remove the protective coating from steel wool, allowing it to rust. When the iron combines with oxygen in this chemical reaction, heat is released.

What You Need:

• Thermometer
• Jar with Lid
• Steel Wool
• Vinegar 

Please note:  All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.

What You Do:

1. Place the thermometer in the jar and close the lid. Wait about 5 minutes then open the lid and read the thermometer.
2. Soak a piece of steel wool in vinegar for 1 minute.
3. Squeeze the excess vinegar out of the steel wool.
4. Wrap the wool around the thermometer and place the wool/thermometer in the jar, sealing the lid.
5. Wait 5 minutes then read the temperature and compare it with the first reading.
6. Chemistry is Fun!

Notes:

1. Not only does the vinegar remove the protective coating on the steel wool, but once the coating is removed, the acidity of the vinegar aids in oxidation (rust) of the iron in the steel. The protective layer on spun steel wool fibers is a thin coat of oil.
2. The thermal energy given off during this chemical reaction causes the fluid in the thermometer to expand and rise up the column of the thermometer tube.
3. In the rusting of iron, four atoms of solid iron react with three molecules of oxygen gas to form two molecules of solid rust (iron oxide):
                4 Fe (s) + 3 O₂ (g) —> 2 Fe₂O₃ (s) 

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Kathleen Carrado Gregar, PhD, Argonne National Labs 
[email protected]
March 2010

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References:  Anne Marie Helmenstine’s About.com website at: http://chemistry.about.com/cs/howtos/ht/exothermic.htm