A pot bubbles and bubbles — and the water keeps getting smaller. Where does it go?
Look at the pot… it bubbles and bubbles on the hot fire. The water is getting smaller, and smaller, and smaller. Soon there is almost none left! So where did all that water go? Ready to guess… does it float UP into the air, or is it all gone for good?
After you watchA pot bubbles and bubbles — and the water keeps getting smaller. Where does it go?
The short answer
The boiling water doesn't disappear — it turns into steam, a kind of floaty invisible air-stuff, and rises up into the air. It's still the same water, just spread out and floating, not gone.
Try this next
- What if you held a cold lid over the boiling pot? Imagine a cold lid up above the steam. Guess first: does the lid stay dry, or get drippy? Watch for water drops gathering on the underside as the steam touches the cold.
- What if you boiled it even longer? Picture the pot left to boil and boil. Guess what's left at the very bottom. Watch the last little bit of water float away too.
The whole story
How it works
Heat makes the tiny bits of water move so fast that they leap off the top of the water and fly into the air as steam. As more and more bits fly off, the puddle in the pot shrinks. The water didn't vanish — it floated up. Higher up, when it cools, the steam can clump back into a little misty cloud you can see.
What people get wrong
Lots of little kids think the water just disappears or 'dries up into nothing.' But nothing is ever destroyed — the water sneaks away as steam and floats up into the air. You can catch it: hold a cold lid over the pot and the steam turns back into water drops.
The catch
Steam is great at carrying water up into the sky, but it's also hot and you can't really see it right above the spout, so it can surprise you. The puffy white cloud a bit higher up is easy to spot — but by then the water has already cooled, so the hottest part is the clear part you can't see.
Questions kids ask
Did the boiling water really disappear?
No! It turned into steam and floated up into the air. Steam is still water, just spread out and floating. None of it is gone for good.
Why does the water in the pot get smaller?
Because little bits of water are leaping off the top and flying away as steam. The more bits that fly up, the lower the water gets.
Where does the steam go after it floats up?
It rises into the air. When it cools down up high, the floaty steam can clump back together into a tiny misty cloud you can see.
Talk about it
- Point at a boiling pot and ask: where do you think all that water is going? Guess together before we look.
- When a puddle dries up on a sunny day, where do you think the water went?
- Have you ever seen the bathroom mirror get foggy after a hot shower? Where did that water come from?
For grown-ups
When water boils, it changes from a liquid to water vapor — a transparent gas — and disperses into the air. The water isn't lost; conservation of mass holds. Just above the spout the vapor is hot and invisible; as it mixes with cooler air it condenses into a mist of tiny droplets, the visible white plume. Hold a cold lid over the pot and the vapor condenses straight back into liquid water, proving it was there all along.
Keep going
What else makes you wonder?
- Where does a puddle go when the sun dries it up?
- If steam floats up into the sky, could it come back down as rain?
- What happens to the water if you put a cold lid on the pot?