Why do fizzy drinks bubble?
The short answer first, then the real reason — and a version for younger kids. Guess before you scroll to make it stick.
✅ Carbon dioxide gas is dissolved in and escapes when opened
But why?
At the factory, CO₂ is forced into the drink under high pressure (Henry’s law: more pressure dissolves more gas). Sealed, the gas stays dissolved. Opening drops the pressure suddenly; the liquid now holds more gas than it can keep, so CO₂ exits — nucleating into bubbles on tiny scratches, fibers, and the glass walls, streaming upward until the drink goes flat.
🧒 For younger kids: The drink has gas SQUEEZED into it. Open the cap — the squeeze stops, and the gas escapes as bubbles!
🤯 Wow fact: The fizzy tingle isn’t just bubbles — the CO₂ reacts on your tongue to make a slight carbonic acid, giving soda its bite.
Good guesses kids make
“Because soda contains tiny rockets” — Fun, but the bubbles are plain gas escaping — no engines aboard.
“Because the liquid is boiling” — Fizzy drinks are cold! Boiling is steam; this is trapped gas at room temperature.
“Because air sneaks in through the cap” — The gas was already inside, dissolved — nothing enters when you open it.
More food & life why questions
- Why does melted cheese go stretchy?
- Why do eggs turn hard when you boil them?
- Why does ice cream give you brain freeze?
- Why does salt melt ice on roads?
- Why does popcorn pop?