Question

when you fill a glass with cold water from a faucet and then let the glass sit undisturbed for two hours, you will see small bubbles sticking to the glass. what are the bubbles? why did they form?

Answer 1

Those bubbles are water vapor molecules that were trying to evaporate out of the liquid water. They formed because after a while, the cold water gained some heat from the environment and this heat was sufficient to provide the energy for the water molecules to escape into the gaseous form from the liquid state.

Answer 2

or the bubbles are air bubbles that were added as the water was being poured from the faucet. As temp rises, gas becomes less soluble in water, so the dissolved air gasses begin to form bubbles.

Answer 3

That works too :P