Where does the boiling water go?

A pot boils and a big white puff billows up — but look right at the spout and there's a clear gap with nothing in it. So is that gap empty? And what is the white cloud, really? Let's hold a cold plate up to it and find out.

1One trick water can do

Water can hide — then come back

You only need two ideas. Watch each one happen:

Hot water spreads out

Heat flings the water bits far apart until they fly off as a gas. They're so spread out your eyes can't catch them — the water is still there, just invisible.

Cool air clumps it back

When the gas cools, the bits slow and crowd together into tiny droplets you can see — a little cloud. Cooling is what makes the water show up again.

2Two looks, same water

The clear gap vs the white cloud

Above a boiling spout there are really two zones. Same water — but they look completely different because of how hot and spread out the water is:

Hot & spread out

The clear gap

Right at the spout the water is a super-hot gas, flung so wide apart it's totally invisible.

Cooled & clumped

The white cloud

A bit higher up it has cooled and clumped into tiny drops — now you can finally see it.

3Your turn — turn up the heat

Make it boil and watch the plume

Drag the heat up and down. Watch the invisible gas pour out of the clear gap at the spout, then turn into the white cloud a little higher up where the room air cools it.

invisible hot gas cooled cloud you see
Turn the heat: a gentle simmer
OFFFULL BOIL

4Now catch the invisible water

Hold a cold plate in the clear gap 🍽️

Here's a cold plate. The big question is about the clear gap right at the spout — the part that looks empty. Guess first, then drag the plate right into it and watch.

Guess before you catch it

You hold a cold plate in the clear gap right above the spout. Will it stay dry or get wet?