A Chemistry Experiment on the Rusting of Iron

Preparing for the Experiment

• A simple controlled experiment on the formation of rust can be performed by placing iron nails into test tubes containing different levels of exposure to air, moisture, and salt. This requires the following:

  4 test tubes with rack

  4 iron nails

  1 rubber plug fitted to the top of a test tube

  Deionized water

  Table salt

  Cooking oil

  Calcium chloride granules

Setting Up the Test Tubes

• Partially fill each test tube to create a specific type of exposure for the nails. Fill one with enough deionized water to cover a nail and then add a nail. Label it "1." Fill another to the same level with deionized water which has been boiled for 15 minutes. Add a nail and pour a small amount of oil in to cover the surface of the water. This will prevent air from reaching the water. Label this tube "2." Fill another tube to the same level with a solution of salt and water. Add a nail. Label it "3." Place the calcium chloride granules into the remaining tube along with the remaining nail. Cover this tube with the rubber plug and label it "4." Leave the tubes alone for at least three days.

What Has This Done?

• By filling the tubes in this way, you have created four distinct environments for the nails.

  Tube No. 1 exposes the nail to both water and air. Tube No. 2 has water, but no air -- the boiling removed the air and the oil keeps new air from getting in. Tube No. 3 exposes the nail to air, water and salt. Tube No. 4 exposes the nail to only air, as the granules absorb the water and the plug keeps new moisture from entering.

Check the Results

• Check on the nails after three or more days. The nails in tube No. 2 and tube No. 4 will not have rusted. The nail in tube No. 1 will have rusted, but the one in tube No. 3 will have rested more. This shows that both air and water are necessary for rust to take place and that salt causes it to spread faster.