1The secret inside the water
Water is hiding air — and ice doesn't want it
You only need two ideas. Watch each one:
Water is full of invisible air
Tap water has air dissolved right inside it. Those tiny bubbles that creep up the side of a glass of water? That's the hidden air slowly sneaking out.
Ice shoves the air out
Ice only fits pure water. As water turns to ice, the freezing edge pushes the air out in front of it. The air has to go somewhere.
2Two ways water can freeze
The trap vs the sweep
It all comes down to how the ice grows. There are two ways, and they treat the air completely differently:
The trap
Ice forms on every side and slams shut in the middle — sealing the air inside as tiny bubbles.
The sweep
One ice edge grows slowly across, pushing the air ahead of it — sweeping it all the way out.
3Your turn — find the hidden air
Stir up the water and watch the air escape
Drag the slider to shake more air loose from the water. Watch the hidden amber bubbles fizz up and pop out — that's air that was dissolved inside the whole time.
4Now freeze it — two ways
Same water, two cups. Which one comes out clear? ❄️
Both cups hold the exact same airy water. The left cup will freeze fast on every side at once. The right cup will freeze slowly, only from the top down. Guess first — then freeze them and watch.
Guess before you freeze
One cup freezes fast on every side at once. One freezes slowly from the top down. Same water in both. Which cup comes out clear?