Re: Why do apples turn brown when they get cut?

Apples have a chemical in them (it's a special chemical called an enzyme) 
that reacts with other chemicals (called phenols) and with oxygen.

The enzyme converts the phenols and the oxygen to another chemical that 
has a brown color.  The enzyme puts the phenol and the oxygen together, 
sort of like the way you can put two lego blocks together.

This chemical reaction can only happen if the apple is cut or bruised 
because otherwise the microscopic apple cells keep the enzyme and the 
phenols in, and the oxygen out, kind of like a plastic bag keeps potato 
chips in your lunch bag from getting mixed with the rest of your lunch.

Do you understand now?