Oxidation of Iron - An example
of a Combination Reaction
Vanderbilt Student Volunteers for Science
Training Presentation
Spring 2010
Introduction
• Oxidation: Oxidation usually occurs when an
element or compound combines with oxygen.
– Apples turn brown after they have been cut and left
exposed to the air.
– Iron is oxidizing when it rusts and turns a reddish
color
• This example of rusting is called a combination
reaction
– Rust = iron oxide
Part 1: Rusting of Iron Filings
1.
2.
3.
4.
Put cotton ball into a
1oz cup and sprinkle
with iron filings.
Sprinkle a small scoop
of salt
Add a squirt of
Hydrogen Peroxide
Set aside and observe
after starting part 2.
*the obvious orange color forms within 2 minutes
Part 2: Steel Wool
1.
2.
3.
4.
5.
Put steel wool into plastic bag
Put plastic bag into cup (line it like a garbage can)
Add a spoonful of salt and the rest of the peroxide.
Feel the bag and note the temperature (Should be
at room temperature)
Measure the temperature again in 1 minute
Steel wool piece
Line like a garbage can
Looking back at Part 1
• Look back at the iron filings.
• Equation: 4Fe + 3O2  2Fe2O3
Before: no rust
After: orange color
Return to Part 2.
1. Measure the
temperature of the
steel wool in the
plastic bag now.
NOTE: Now at 90
degrees.
Conclusion
• The reaction in this experiment was a
COMBINATION REACTION
• The temperature of the iron filings plus
peroxide plus salt mixture increases, so
the reaction is EXOTHERMIC.
Clean Up
• Wipe thermometers and bring them back.
• Seal plastic bags and throw away in trash
can.
– If the school does not want you to put it in
their trash, put all the bags in a larger bag and
bring back to the VSVS lab.