Have you ever noticed that before you open it, you can’t see any bubbles in a bottle of soda or seltzer? They only appear once you open the bottle and take a drink or pour the liquid into a glass. In this experiment, you’ll learn where those bubbles come from by dropping two different objects—a smooth marble and a rough raisin—into glasses of seltzer and observing what happens.
Make a prediction: Which glass of seltzer do you think will have more bubbles, the one with the marble or the one with the raisin? Why do you think so?
Fill both drinking glasses with cold seltzer until they are about ¾ full (be sure to fill both glasses to the same level).
Observe your results: Let go of marble and raisin at same time, letting them drop into their respective glasses. Observe what happens for 30 seconds.
(Don’t read until you’ve finished the experiment!)
When we embarked on this effervescent experiment in the Recipe Lab, we observed lots of bubbles right away in the glass with the raisin. There were fewer bubbles in the glass with the marble, but we observed bubbles for a longer time.
The bubbles in seltzer or soda are made of carbon dioxide gas. When seltzer is in a sealed bottle, the gas is dissolved in the liquid—you can’t see it. When you open the bottle, some of the dissolved carbon dioxide turns back into a gas and escapes as bubbles. But to get the bubbles really popping, you need some help.
Just like Clark Kent needs a phone booth to change into Superman, dissolved carbon dioxide needs a special place to become a bubble, called a nucleation (“new-clee-AY-shun”) site. Bubbles form at nucleation sites and rise through the beverage until they pop at the surface. A nucleation site can be anything from a tiny fiber from a towel to a speck of dust to the surfaces of the marble and raisin.
The wrinkly raisin has more nucleation sites than the smooth marble. And more nucleation sites means more bubbles. But there’s only so much carbon dioxide dissolved in the seltzer water. Eventually, the bubbles slow down because there’s not much carbon dioxide left. The gas is used up more quickly when there are more nucleation sites, as in the glass with the raisin. In the glass with the smooth marble, there were fewer bubbles at any given moment, but the seltzer stayed bubbly for longer.
Which do you think will be bubblier: cold or warm seltzer water? Here’s how to find out: Gather two equal-sized sealed bottles of plain seltzer. Place one in the refrigerator until it’s really cold. Leave the other at room temperature. Grab the bottles and a friend and head outside (this could get messy!). At the same time, each of you should open one seltzer bottle. What happens?
We’ll bet the bottle of room temperature seltzer was MUCH fizzier than the cold seltzer. That’s because cold water can hold a lot more carbon dioxide than warmer water, so it has fewer bubbles right away. More of the carbon dioxide escapes as gas bubbles at room temperature when you open the bottle—this causes the seltzer to shoot out of the bottle (and get someone very wet!).
The takeaway: When it comes time to open any bubbly beverage, get that bottle nice and cold, or be prepared to get wet!