Water droplets form on the outside of a glass of cold soda because water vapor in the air condenses into liquid when it touches the cold surface of the glass.

What’s Really Happening?

When you pour cold soda into a glass, the glass itself cools down to a temperature lower than the surrounding air. The air around us always contains some water vapor (invisible gaseous water), especially on warm or humid days.

As this moist air comes into contact with the cold surface of the glass, it loses heat to the colder glass and cools down. If the glass is colder than the air’s “dew point” (the temperature at which air can’t hold all its moisture), the extra water vapor condenses into tiny liquid droplets on the outside of the glass.

Those droplets are from the air, not leaking soda. They’re new liquid water formed by condensation.

Key Concepts (Mini Sections)

1. Condensation, Not Evaporation

  • Condensation is when a gas (water vapor) turns back into liquid water as it loses heat.
  • The statement “water droplets form on a cold soda can due to evaporation” is false; it happens due to condensation instead.
  • Evaporation is the opposite process: liquid water gaining energy and becoming vapor (like puddles drying).

2. Role of Temperature and Dew Point

  • The cold soda cools the glass; the glass then cools the air right next to it.
  • When that thin layer of air is cooled below its dew point, it can no longer “hold” all its water vapor, so some of it condenses into droplets.
  • Once the drink warms up and the glass is no longer much colder than the air, the droplets stop forming and may evaporate again.

3. Why You Notice It More in Summer

  • On hot, humid days, the air contains a lot of water vapor, so there’s more moisture available to condense on a cold glass or bottle.
  • That’s why your cold soda “sweats” dramatically in summer but much less in cool, dry weather.

A Simple Way to Visualize It

Think of the air around your glass as a sponge soaked with invisible water vapor. When the air touches the cold glass, it’s like squeezing that sponge by cooling it down: some of the water has to come out, and it shows up as visible droplets on the glass.

TL;DR:
Water droplets appear on the outside of a glass of cold soda because moist air touching the cold glass is cooled below its dew point, so water vapor condenses into liquid droplets on the glass surface.

Information gathered from public forums or data available on the internet and portrayed here.