Field Notes EXTRA #4 · We're Not Quite Finished with Floating Ice

We're not quite finished with floating ice.

In Field Notes 11, we posed the question:

In a brim-full glass of water with ice floating in it, what happens to the water level when the ice melts?

We showed that Archimedes' Principle guaranteed that the water level would stay the same.

A floating object displaces an amount of water equal to its own weight. So when ordinary ice melts, it simply fills the space it had already displaced.

We ended Field Notes #11 with a Pop Quiz:

We gave you the answer.

But we didn't actually do the experiment.

So we did.

We froze 16 pennies—40 grams of copper and zinc—inside another ice column and floated it in a cylinder filled to the brim.

See what happened below:

Then we tried the opposite.

Instead of putting something heavy inside the ice, we put almost nothing inside it.

Air.

We froze a hollow column of ice with a giant pocket of air trapped inside.

It floated spectacularly high. It was amazing. We filled the cylinder to the brim and watched it melt completely.

Unfortunately, the camera didn't.

We thought we recorded the entire melt as a time-lapse. Apparently, my iPhone had other ideas.

So for once, you'll have to trust us. 😉

The water level stayed the same.

Honestly.

Last time, we put something heavy inside the ice. This time, we put almost nothing inside it.

In both cases, Archimedes told us exactly what to expect, and in one of those cases, we filmed it.

Apparently, we still aren't quite finished with floating ice. 😁