Oxidation

When the Statue of Liberty was first gifted to the United States from France, it was a much different color than it is today! The statue is made out of a metal known as copper. However, over time, the statue was exposed to the elements of the outside world and turned green! This happens due to oxidation. Oxidation is the process by which an object gains oxygen. Due to a chemical reaction between the copper, water, and air, the statue turned green. This green color is called patina and is just a layer on top of the copper. It keeps the integrity of the copper metal intact and prevents any further damage. On a much smaller scale, we can see oxidation with an apple! When we slice it in the morning and then go to eat our lunch in the afternoon, we see thatthe apple turns brown. This occurs because the apple contains an enzyme that undergoes a chemical reaction with oxygen. Normally this enzyme is protected from exposure because there is an apple peel – but when sliced, that peel can’t protect the apple. Try this experiment below to see if you can slow the oxidation process for an apple at home!

Materials: 1 apple, Vinegar, Lemon Juice, Water, Milk.

Directions: Take 6 plastic ziploc bags and write on each one the liquids that you will use (mentioned above). On one bag, write that it is a control and no liquid was added. Cut the apple into slices and put one slice in the bag. Pour in enough liquid to cover the apple. Be patient and observe what happens! After an hour you will notice that some liquids prevented the apple from turning brown. Why does this happen?

How It Works: The lemon juice works best to prevent oxidation because it is full of ascorbic acid! This acid will react with the oxygen in the air before the flesh of the apple has a chance to. This prevents the apple from experiencing the chemical reaction and stays nice and fresh.

Want more? Research it! Fruit browning is an example of an oxidation and reduction reaction where electrons are being transferred between two things. What are other types of oxidation reduction reactions?