Y空氣入左apple到,個蘋果會change colour??

apple contains rich iron...
when the apple is cut in to half and expose in the air,
the oxygen in air will react with the iron in apple(rusting).

chemical equation:
4Fe+2O(2)-->2 Fe(2)O(3)

the apple will then become yellow in colour.
the yellow thing is the iron(3)oxide.

becaus個apple氧化囉~^^~