When a tea bag kept in boiling water the colour of changes?

The color of a tea bag changes when placed in boiling water because the hot water extracts the pigments from the tea leaves. These pigments are called polyphenols and are responsible for the color, flavor, and antioxidant properties of tea.

Here's a breakdown:

* Unbrewed tea leaves: The polyphenols are bound within the leaves, giving them a natural color (often a greenish-brown).

* Boiling water: The heat breaks down the cell walls of the tea leaves, allowing the polyphenols to dissolve into the water.

* Infused tea: The dissolved polyphenols in the water create the characteristic color of the tea. This color can vary depending on the type of tea, with black teas being darker than green teas.

So, the color change isn't the tea bag itself changing, but rather the water being colored by the pigments released from the tea leaves.