Final answer:
Bubbles and foam in drinks like soda or beer deliver a 'fizz' sensation caused by the release of carbon dioxide (CO2) when the pressure is reduced upon opening the container.
Step-by-step explanation:
Bubbles and foam deliver a sensation known as fizz to the drinker. This fizz is the result of carbon dioxide (CO₂) gas, which when dissolved in a liquid under high pressure, creates a large amount of dissolved CO₂. Upon opening a carbonated beverage, like soda or beer, the pressure is reduced, causing the dissolved CO₂ to come out of solution and form tiny bubbles. These bubbles cause the liquid to become effervescent or fizzy, providing a pleasing sensation as they burst in the mouth. Over time, if a carbonated beverage is left open, it becomes "flat" as it loses CO₂ and its concentration diminishes.