Carbonated drinks like soda, beer, and champagne contain carbon dioxide dissolved in liquid. Observe how, when you open a bottle of carbonated drink, its contents form gas bubbles. Carbonated drinks are sealed and bottled with a mixture of air and carbon dioxide under 3 to 4 atm. The amount of carbon dioxide dissolved in the drink increases many times because of the increased pressure. When the cap of the bottle is opened, the pressurized gases escape and the pressure drops to about 1 atm. It is the dissolved carbon dioxide coming out of the mouth of the bottle that causes the fizzing sound (effervescence). In this case, the solubility of gases in liquid is affected by the pressure change.