Pouring and Siphoning a Gas

When most students hear the word “fluid” they automatically think of liquids—something that flows with no rigid shape of its own, something that can be poured from one container into another. Gases are fluids, too. Perhaps it is because of their invisible nature or their lack of any self-defined boundaries that gases maintain such a low profile. Thus it is certainly an eye-opener when students see (or rather, don’t see) a dense gas such as carbon dioxide being poured or even siphoned from one container into another.