Bubbles formed in standing water in glass

Question

I kept a cold standing water in a glass for a while to warm it up. After a while I returned to see that small minute bubbles have formed in the glass. On closer inspection, the bubbles seem to not float to surface like fizzy drink but they have sticked to surface (mostly at bottom) while some but lesser bubbles have sticked to vertical surface of glass. I haven't seen or paid attention to this phenomenon, and also water is drinking water so it shouldn't be contaminated. I can't think of any physical phenomenon for this? So can anyone try to figure the root cause for this?

Answer 1

It is more like bubbles coming out of fizzy water than boiling. Water often has air dissolved in it. If you let it sit, it can come out of solution.

This happens at the surface, where the water contacts another material. You would not notice it if molecules of air enter the air above the water.

Bubbles tend to start on minute imperfections or foreign substances on glass. A microscopic crack will do. Once started, air tends to join an existing bubble rather than start a new one.

Bubbles on the side can slide sideways and rise to the surface. A bubble on the bottom would have to let go. They tend to stick to the glass, so sliding is easier.

Answer 2

Air in pits and crevices in the glass walls act as nucleation sites for the exsolvation of air in water. Air is less soluble in warm water than cold, so as the water warms up it becomes supersaturated with air, and it comes out of solution at the pit locations.

If you shoot a beer commercial in which beer is poured into a tall, sparkling new glass, you want the beer to produce bubbles. If the glass is new, it will have few pits and crevices in its surface and so few bubbles will form. To remedy this, you can put some big ball bearings in the (empty) glass and shake them around a bit, then remove the bearings and pour in the beer. You'll have lots of bubbles for the camera now. Yum!