George Zaidan set out to capture the intricate process of water freezing into crystal clear ice. Instead, his experiment in slowly freezing a drop of water reveals a phenomena he didn’t expect: instead of freezing completely clear along the bottom, “ice crystals exploded into the drop.” And it happened again and again.
“So now, instead of this video being about clear ice, it is gonna be about how water freezes. And it turns out that this thing that we do in our freezers every single day is gonna take us right to the edge of scientific understanding.”
In this Reactions video from ACS, educational science producer, chemist, and author Zaidan takes a closer look at how ice forms, including the hexagonal lattice structure of ice, the presence of impurities (minerals, salts, organic matter, etc) and dissolved gases (carbon dioxide, oxygen, nitrogen) that seem to “appear out of nowhere,” the differences between slow and quick freezing, what those “fractal forests” he kept observing are.
“So after freezing about a thousand of these droplets, I noticed two really cool things: Thing one is that the pattern of the fractal forest was always similar, but never exactly the same, even when I froze and thawed and refroze and thawed and refroze the same droplet over and over again.
“So I popped into the scientific literature and I discovered that these things are called dendrites and that science has known about them since at least 1611…”
Dendrite, from Ancient Greek, refers to the tree-like branching of these structures. “In the droplets I’m freezing,” he adds, “all the dendrites would have likely come from a single nucleation point, not multiple ones.”
“I said at the beginning of this video that these dendrites would take us to the very limit of scientific understanding. And to reach the limit, you have to ask a super basic question, which is just “why?”—why do these dendrites happen?”
What’s happening on the molecular level at that initial inception point where the freezing begins in everyday water all over the planet?
ACSReactions also suggests some scientific observation:
“The distribution of bubbles and impurities in a piece of ice can potentially tell you a lot about how it froze. So if you look at the ice cubes in your freezer, are they clear on the outside and cloudy in the middle? Clear on top and cloudy at the bottom? Uniformly cloudy throughout? Tell us what you find.”
Watch these handpicked videos about ice next:
• What’s In a 20,000 Year-Old Cube of Ice?
• Soap bubbles freeze in the snow, a macro 4K video
• Instant Ice Crystals – The Secret Life of Ice
• Why do ice cubes crack in drinks?
• The scientist that grows ‘identical twin snowflakes’
• Ironing and drilling into the clearest ice in the world
And: Why is water one of the weirdest things in the universe?
Bonus activities: Melting ice with salt and how to grow snowflakes in a bottle.
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