When a glass of water is left undisturbed overnight, tiny bubbles often appear, clinging to the sides or rising slowly to the surface. This natural phenomenon reflects the subtle interactions between water and its environment. Understanding why these bubbles form reveals insights into the physical properties of water.
Water’s Hidden Air
Water, especially tap water, contains dissolved gases that are not immediately visible. These gases, primarily oxygen and nitrogen from the atmosphere, become incorporated into the water. Just as sugar can dissolve in water, so too can gases, occupying the tiny spaces between water molecules. This process, known as gas solubility, means that water is a solution containing various dissolved substances, including these atmospheric gases.
The amount of gas that can dissolve in water depends on several factors, including pressure and the specific type of gas. Under normal atmospheric conditions, water absorbs and holds a certain quantity of these gases. These dissolved gases are imperceptible to the naked eye when they are fully integrated into the liquid. They remain dissolved until conditions change.
The Overnight Cooling Effect
The formation of bubbles overnight is directly linked to changes in water temperature. Water drawn from the tap is often slightly warmer than the ambient room temperature. As this water sits in a glass, it gradually cools to match the temperature of its surroundings. The solubility of gases in liquids decreases as the temperature of the liquid decreases. This means that cooler water can hold less dissolved gas compared to warmer water.
As the water cools, the excess dissolved gases, unable to remain in solution, begin to escape. These gas molecules coalesce, forming microscopic bubbles. These bubbles often nucleate on imperfections within the glass or on tiny dust particles, growing larger as more gas molecules accumulate. The gradual nature of this cooling explains why the bubbles become noticeable over several hours.
Drinking Water with Bubbles
The bubbles that appear in water left overnight are simply air that has come out of solution. These bubbles are harmless and do not indicate issues with water quality or safety. The water remains perfectly safe to drink, as the escaping gases are the same ones naturally found in the air we breathe.
If left undisturbed, these bubbles will eventually rise to the surface and pop. The presence of these bubbles is a normal physical process, confirming the water’s interaction with its environment rather than signaling contamination. Consuming water with these bubbles poses no health risk.