Why do apples get dark after being cut?

Question

what is the chemical reaction going on? changing color

Answer 1

Technically the apple is turning brown due to oxidation. As the cells in the apple are cut and exposed to oxygen the chemical reaction causes it to change color. You can avoid this by placing the cut apple pieces in slightly acidulated water(water with a little lemon juice-the acid) just a little. The same effect occurs with potatoes, they turn black. You can prevent this by submerging cut potatoes in plain water. Seriously.  

Answer 2

This is from oxidation(they are rusting)Put some lemon juice or vinegar on them to stop this.I recommend rice vinegar.