What causes Lipton iced tea to dissolve?

Iced tea can be made from hot tea that has been chilled; or by soaking tea leaves in cold water for a longer time.

Because iced tea is made with boiling hot water, the answer has to do with the solubility of the tea leaves in hot water.

The tannins cause tea to be slightly bitter. Because the molecular components of tannins are large and complex, they do not dissolve in cold water. The caffeine molecules, however, are smaller and lighter and are able to pass through the semi-permeable cell wall with ease. So, although the flavor in the tea bag takes longer to extract in cold water, the caffeine moves in and out of the bag quickly, no matter what the water temperature.

When hot water comes in contact with the tea bag, the heat accelerates the rate of extraction. The larger tannin molecules are able to move quickly enough through the semi-permeable cell wall of the tea bag's membrane that the two types of molecules seem to be extracted simultaneously: the water is almost instantly brown and bitter tasting.