Why does the outside of a glass iced tea some times get moist?

The outside of a glass of iced tea gets moist due to a phenomenon called condensation. Here's how it works:

1. Warm, humid air: The air around the glass of iced tea is typically warm and contains some moisture (humidity).

2. Cold surface: The glass of iced tea, filled with cold liquid, is much colder than the surrounding air.

3. Water vapor cools: When the warm, humid air comes into contact with the cold glass, the water vapor in the air cools down.

4. Condensation: As the water vapor cools, it loses its ability to hold as much moisture. This excess moisture condenses into tiny water droplets that form on the cold surface of the glass, making it appear wet.

In simpler terms: Think of it like when you see your breath on a cold day. The warm, moist air from your lungs cools in the cold air, causing the water vapor to condense and become visible. The same principle applies to your iced tea glass.