Have you ever wondered why fizzy drinks make you burp? Read on to find out and try a science activity to demonstrate!
Fizzy drinks are fizzy because they have carbon dioxide gas pumped into them under high pressure. If you have a SodaStream at home, you’ve probably seen how adding the gas makes water fizzy. Fizzy drink bottles are tightly sealed so no air can escape, but when you open the cap, the pressure drops and the carbon dioxide escapes. This is why fizzy drinks go flat over time.
When you drink a fizzy drink, it travels into your stomach. The inside of your body is around 37 degrees. When gas warms up, it expands and spreads out to fill all the available space. As the gas builds up, it pushes against the top of your stomach. To stop the stomach from inflating too much, you burp to let the trapped gas escape.
We can model burping with fizzy water, a balloon and a bottle! The bottle represents the stomach. As the fizzy water warms up, the carbon dioxide bubbles expand and escape from the water, inflating the balloon!
Why Do We Burp Demonstration
You’ll need
A bottle of fizzy water – unopened
A bowl of warm water ( not boiling )
A Balloon
Instructions
Carefully open the bottle of fizzy water and place the balloon over the bottle’s mouth.
Gently swirl the water around the bottle. You should see gas bubbles rising and starting to inflate the balloon.
Carefully place the bottle in the bowl of warm water (this represents a warm tummy). The increased temperature should help the gas bubbles escape the water more quickly, making the balloon inflate more.
Gently pull the balloon off the bottle and let the gas out with a burping noise.
WARNING – use warm, not hot water, and an adult should supervise this activity.
What’s happening?
Fizzy water contains dissolved carbon dioxide gas.
When the fizzy water enters your tummy, it warms up. Warm liquids can’t hold as much gas as cold liquids, so the gas breaks free and builds up inside the balloon.
When you burp, the sphincter muscle at the top of your stomach opens to let out gas. In this activity, releasing the balloon mimics the sphincter opening.
Why do fizzy drinks make you burp? Instruction Sheet
Extension Tasks
Keep one bottle in the fridge and one in warm water, investigate to find out which inflates a balloon the fastest.
Compare fizzy water with a sugary fizzy drink.
Last Updated on October 7, 2026 by Emma Vanstone
