Steel Wool in Vinegar!

Key Concepts

Materials: 
1                          extra fine steel wool
1 container    white vinegar
1                          ​saran wrap
1                        ​  handheld thermometer
1                       ​   glass or beaker
1                        ​  large bowl
1                      ​    camera (phone camera is fine)

RECOMMENDED:
Goggles
Gloves
Apron

Activity Directions:
  1. Take a picture of the steel wool. We’ll need this picture for reference later.
  2. Wrap the steel wool around the thermometer and place the steel wool in the glass. 
  3. After a minute, or until the temperature reading on the thermometer settles, record the temperature by taking a picture of the reading on the thermometer.
  4. Pour some vinegar into the bowl, so that the vinegar is deep enough to soak most of the steel wool.
  5. Remove the thermometer from the steel wool. Take the steel wool from the glass and soak it into the bowl of vinegar. 
  6. After about 5 minutes, take the steel wool out of the vinegar.
  7. Give the steel wool a few squeezes, then wrap the steel wool around the thermometer and place it in the glass. 
  8. Cover the glass, thermometer, and wool as airtight as possible with saran wrap. 
  9. After a minute, or until the temperature reading on the thermometer settles, record the temperature by taking a picture of the reading on the thermometer.
  10. Note that the temperature has increased!
  11. Remove the thermometer from the steel wool and take a picture of the steel wool now. 
  12. Compare the steel wool from before the experiment and after the experiment and note the color change. 
 
Discussion Questions & Science Explanations:
  1. What is stainless steel?
    1. Steel is an alloy made up of mostly iron with some carbon added to improve its material properties. 
    2. Ordinarily, when steel is exposed to air, a chemical reaction occurs in which iron and oxygen combine to form a compound called iron (III) oxide, which we call rust. 
    3. However, stainless steel contains an element called chromium, which forms a protective layer that prevents oxygen from bonding with the iron molecules in steel and forming rust. 
  2. Why does the steel rust even though it’s “stainless?”
    1. The vinegar in the bowl contains a compound known as acetic acid, which corrodes away the protective layer. 
    2. The iron is then exposed. When we place it in the empty glass, the oxygen in the air can react with the iron to produce rust, which has a reddish-brown color.
  3. Why is the steel wool warmer after being soaked in the vinegar? 
    1. As the iron combines with oxygen to form rust, the reaction naturally releases heat energy. 
    2. Reactions that release energy in the form of heat are classified as exothermic reactions. As you might have guessed, reactions that absorb heat energy from their surroundings are classified as endothermic reactions. 
  4. Is this a chemical reaction?
    1. A chemical reaction occurs when the molecular bonds of a substance change. Changing the physical properties of a substance, such as state of matter, isn’t a chemical reaction because the substance is still the same. Some common examples of each include: burning wood (chemical), cooking an egg (chemical), ice melting (physical), cutting paper(physical), mixing play-doh (physical). 
    2. The rusting of the steel is a chemical reaction because the chemical bonds in the reactants are broken and they change into different substances during the reaction. Here, iron and oxygen are reacting to form rust. 

Additional Experimentation:
  1. During step 8, watch the temperature on the thermometer. Can you spot it rising? ​
Suggested Video: https://www.youtube.com/watch?v=MEvYVxXHEGY 

​Published 8.28.2020

Author: Alex Zhang