Why do bubbles form around a straw when it is inserted into a carbonated drink?

Answer 1: 

Carbonated drinks are supersaturated aqueous solutions of carbon dioxide in closed bottles. The solubility of carbon dioxide in carbonated drinks strongly depends on pressure and temperature; the solubility being higher at higher pressures and lower temperatures. Any changes in pressure or temperature of the solution would correspondingly affect the carbon dioxide concentration in the solution. When a straw is immersed in the carbonated drink, the temperature of the straw being higher than the solution, it results in an increase of the temperature of the solution around the straw. Consequently, some of the gas would be liberated from the solution, as the solubility of the carbon dioxide is lower at the higher temperature. The straw provides an adsorptive surface for the exiting carbon dioxide molecules to sufficiently pile up to form bubbles and hence bubbles appear on the straw when it is immersed in carbonated drinks.

Answer 2:

Carbonated drinks are saturated solutions of carbon dioxide under high pressure (a few times higher than atmospheric pressure). When the chilled soft drink bottles are uncorked, the pressure within the bottle decreases and the temperature of the soft drink increases gradually.Due to these two reasons, the solubility of carbon dioxide in the soft drink decreases, leading to effervescence and escape of carbon dioxide.By inserting a straw, the solubility of carbon dioxide around the immersed part of the straw decreases and mild effervescence and bubbles are formed on the straw and the bubbles stick to the straw due to adhesive forces.Plastic straws have a specific property to adsorb bubbles. This property is more significant in PET (poly ethylene terephthalate) and hence these bottles serve as good containers to store aerated drinks to retain flavor and fizz. Some of us can try and see whether straws made of glass can adsorb bubbles just like plastic straws.

Source: thehindu.com