Solar energy bottle scraping.

It must be a chemical change, because compressed air is not needed in beer. When beer is fermented, it will produce a part of carbon dioxide, which is easily soluble in water and forms carbonic acid. The pressure of beer lid is only 1-2 times of the standard atmospheric pressure, otherwise it will explode as soon as it is opened, and it is difficult to open it. When the lid is opened, the pressure in the bottle is reduced. Because carbonic acid is very unstable, it can be easily decomposed into water and carbon dioxide when the pressure changes, so a large amount of carbon dioxide overflows.