Experiment

1. Place a dime over the mouth of a glass bottle.
2. Put the bottle (with the dime covering the mouth) inside a freezer. You’ll need several hours, because the colder the bottle is, the better burps it will have!
3. Remove the bottle from the freezer.
4. Dip one end of a straw into a glass of water. Once part of the straw is submerged in the water, cover the other end with your thumb.
5. Withdraw the straw from the water, and you’ll have water trapped inside the straw.
6. Position the water-filled straw over the dime atop the bottle.
7. Remove your thumb from the end of the straw, allowing the water to pour onto the dime.
8. Sit back and observe! The dime is lifted off of the mouth of the bottle by a burp from inside the bottle. Awesome!

How Does It Work?

How in the world can a bottle burp like that? The secret lies in the properties of two things: water and air.

When you place the dime over the mouth of the bottle, you create a seal (albeit an imperfect one). That means that the air in the bottle is going to stay in the bottle, for the most part, and the opposite goes for the air outside of the bottle. Once you put the bottle in the freezer, the air particles inside of the bottle begin to slow down and become more dense. This means that there is low air pressure inside the bottle. Once you remove the bottle, you expose the air inside to a much warmer climate. The increase in temperature allows the air inside the bottle to quickly expand, raising the pressure inside.

Dropping water on top of the dime creates a slightly better seal than the dime does on its own. This seal is created by hydrogen bonds between molecules of water. These hydrogen bonds create cohesion and adhesion. Cohesion is the act of the water molecules clinging to each other, while adhesion is the act of the water molecules clinging to the mouth of the bottle.

With a slightly better seal, created by the water, you can see the expanding air within the bottle trying to escape through the mouth of the bottle. This increased air pressure pushes against the watery seal and lifts the dime up off of the mouth of the bottle… BURP! The hydrogen bonds break, and the dime goes back onto the mouth of the bottle.