* Physical Change: A physical change alters the appearance or form of a substance but doesn't change its chemical composition.

* Chemical Change: A chemical change results in the formation of new substances with different properties.

When you add water to iced tea, you're simply diluting the tea. The tea molecules are still the same, they're just spread out over a larger volume of liquid. This makes the color appear lighter, but the tea itself hasn't undergone a chemical transformation.

Here are some other ways to think about it:

* Reversible: You can easily reverse the process by letting some of the water evaporate, concentrating the tea again and returning it to its original color.

* No New Substances: The water and tea remain the same substances, just mixed together.

Let me know if you have any other science questions!