I have a science expo I i need a more kid way to say the "why" part of it?

My science experiment is called Drinkable Iron... you add tea into pineapple, apple, white g, and cranberry juice. Then, wait two hours and there is some except for the apple juice. Unless you wait another 5 hrs. I don't understand why... and my teacher (Mrs.Bloch) said that you can't sound like and encyclopedia!...