Bubbles form in water primarily because of dissolved gases like nitrogen and oxygen that come out of solution when conditions change. When water is colder and under pressure, it can hold more dissolved gases. As the water warms to room temperature or the pressure drops, the gas solubility decreases, causing the gases to come out and form bubbles. These bubbles tend to form on microscopic imperfections or rough spots on surfaces within the water container, where gas molecules gather and nucleate into bubbles that eventually rise to the surface.
In summary:
- Water contains dissolved atmospheric gases.
- These gases are more soluble in colder water under higher pressure.
- When water warms or pressure falls, dissolved gases escape.
- Gas molecules collect at rough spots or imperfections, forming bubbles.
- Bubbles grow and float upward to the surface.
This is why bubbles often appear when water stands still in a glass at room temperature after being poured cold from the tap.
