This one question, asked of us by an 11 year old friend of Letterbox Lab, has a few interesting questions wrapped up in it.
Why do bubbles come out of fizzy drinks?
Carbon dioxide is the gas responsible for the fizz in fizzy drinks. This carbon dioxide stays dissolved in the drink because the bottle contains a lot of pressure and a liquid can hold more gas if it’s under pressure. You feel this pressure being released when you open a fresh bottle of pop.
Then you pour your fizzy drink into a glass. The high pressure that was once holding the carbon dioxide in the liquid is now gone. There is more carbon dioxide in the drink than the drink can hold so the carbon dioxide comes out as bubbles. But, the gas doesn’t all come rushing out at once.
Why do the bubbles come from the bottom?
Instead of instantly bubbling out of the drink the gas bubbles out quite slowly at the bottom and sides of the glass. This is because bubbles are not easy to make. You can think of it like this, the little carbon dioxide molecules want to get out of the drink but they need a few of them to get together and make a bubble before they can escape. They are all randomly jiggling around inside the liquid so it’s not very often that enough of them stick together to make a bubble.
The bottom and sides of the glass have tiny little imperfections on them, microscopic dents and scratches. There is already a tiny bubble of gas trapped in these imperfections. When a carbon dioxide molecule collides with this bubble they merge making a bubble that is too big for the scratch or dent to hold. So the bubble breaks in half, some of it stays behind and some of it floats up to the surface and pops. Because some of it stays behind the same thing can keep happening over and over again. This is why you see a stream of little bubbles coming from certain points on the glass. Some glasses are actually designed to have these little scratches to make more bubbles.
Why don’t the bubbles run out?
The science says that there is only a certain amount of carbon dioxide in the liquid and once it’s gone the bubbles will stop. This will take a long time because the events described above are pretty slow so it might appear that the bubbles don’t run out because you have finished your drink before the carbon dioxide has had time to get out.
But you shouldn’t take our word for it when it’s easy to do some experimenting yourself. Pour yourself a glass of something fizzy and leave it undisturbed. Do the bubbles ever stop? How long does it take? If so, can you think of a way to speed up or slow down the process? You can get an idea of how much carbon dioxide is in the drink if you put the glass on some weighing scales – the weight should go down because even bubbles have weight. Or you could try putting a balloon over the neck of a bottle, will the bubbles inflate the balloon?
Happy experimenting.
Would you like to spend time with your children doing something that’s fun and educational for them and hassle-free for you?
Letterbox Lab is a monthly science kit that arrives through your letterbox containing everything you need to perform incredible experiments with your children.
Your children will love it. It’s colour changing, fizzing reactons, slimes, things that glow in the dark, making helicopters and catapults. All with beautifully illustrated comic-style instructions that they will actually enjoy reading.
You’ll love it because it’s so easy. It just arrives at your house with everything you need to do all the experiments. Unlike other science kits there’s no looking in the back of cupboard for cream of tartar or figuring out where you can buy propanol on a Sunday afternoon. You just open the box and get started with ease.
Find out more about our unique series of science kits here
Take a look at our other Halloween science activities: Glow in the Dark Slime here
As a seasoned science enthusiast with a deep understanding of the principles behind fizzy drinks and bubble formation, let me dive into the fascinating world of carbonation and its delightful effervescence.
First and foremost, the key player in the fizz of fizzy drinks is carbon dioxide (CO2). This gas is responsible for the bubbles that dance in your soda. The reason carbon dioxide stays dissolved in the liquid is due to the high pressure within the bottle. When you crack open a fresh bottle of pop, you're essentially releasing this built-up pressure, allowing the carbon dioxide to escape.
Now, why do these bubbles appear from the bottom of the glass rather than instantly emerging throughout the liquid? This phenomenon is rooted in the nature of bubble formation. Carbon dioxide molecules, eager to escape the liquid, need to gather and form a bubble before making their grand exit. However, this process isn't instantaneous. The microscopic imperfections on the bottom and sides of the glass, like tiny scratches and dents, play a crucial role. These imperfections already contain small bubbles of gas. When a carbon dioxide molecule collides with these imperfections, it merges with the existing bubble, creating a larger one that rises to the surface and pops. This process can repeat, leading to a stream of bubbles emanating from specific points on the glass. Some glasses are even intentionally designed with these imperfections to enhance bubble production.
Now, you might wonder why the bubbles don't run out. The scientific explanation lies in the finite amount of carbon dioxide dissolved in the liquid. As the events described above unfold relatively slowly, it may seem like the bubbles are endless, especially since you might finish your drink before all the carbon dioxide escapes. To test this, you can conduct a simple experiment. Pour yourself a fizzy drink, leave it undisturbed, and observe if the bubbles eventually stop. You can even measure the carbonation by placing the glass on weighing scales – the weight should decrease as the bubbles escape, confirming that even bubbles have weight.
In conclusion, the magic behind fizzy drinks lies in the intricate interplay of pressure, carbon dioxide, and microscopic imperfections in the glass. Next time you enjoy a fizzy beverage, you can appreciate the science bubbling beneath the surface. Happy experimenting!
