More playing with a vacuum pump.

In this post, we talked about how decreasing the pressure on water can make dissolved gases come out of solution. But what happens if you suddenly increase the pressure again?

This is the same movie as in the previous post, just to remind you of what we did: We decreased the pressure and then let it increase again quickly (you hear the ssssssssssss when the air is streaming back into the bottle).

So to show it in one picture, what happens is basically this:

Bubbles under low pressure (top) and high pressure (bottom). Screen shots from the movie above.

The lower the pressure, the larger the bubbles. When you let the air back into the bottle, the bubbles collapse (or shrink, if you want to be less dramatic).

That reminds me that I really need to film a movie similar to the one below where one can clearly see how bubble size increases the closer the bubbles come to the surface.

Isn’t it awesome to realize that the more you film and write and think about adventures in oceanography and teaching, the more ideas you have of what you want to do next? :-)

A simple experiment to show that there are really gases dissolved in water.

Luckily, my parents like to play at least as much as I do. So when I got back from doing “real science” in Bergen the other day, they picked me up at the airport and showed me their latest toys: Vacuum pumps! [edit: Not really vacuum vacuum, but at least much lower than atmospheric pressure. And apparently those pumps are sold with the original purpose of re-sealing wine bottles]

Vacuum pumps are great to show that there are actually gases dissolved in water, because oftentimes that isn’t all that obvious. But when the pressure of the head space of a bottle is decreased, gases that were happily dissolved under atmospheric pressure start coming out of solution.

Gas being bubbled out of water by decreasing the pressure of the head space of the bottle.

Here is a comparison of normal tap water and sparkling water (sparkling water obviously containing much more dissolved CO2 than tap water, hence more bubbling).