Return Home

Jad Grows Ice, With One Finger

Thursday, March 13, 2014 - 02:18 PM

Okay, so it's not reallllllyyy ice, as you know ice to be.


BUT, while we were at Rockefeller University, seeing just how fast water can change into ice for our podcast, Super Cool, our lab team showed us something else crystallizing -- sodium acetate.

What the hell is happening in that petri dish?

I asked Alexander Petroff, our intrepid lab leader (and also the Raymond and Beverly Sackler Fellow, at Rockefeller University) to explain:

"The basic idea is exactly the same as the super cooled water. In the case of the ice, the water was cooled below its freezing temperature. Because there was nothing for large ice crystals to form around, the water stayed a liquid until we gave it something to freeze around. In the case of the sodium acetate, we dissolved more sodium acetate into the water than the water could hold. However, because there was nothing in sodium acetate crystals to form around, all of it stayed dissolved until Jad put his finder into it. The sodium acetate crystals formed around Jad's finger, just like at night, extra water forms as dew around things like spider webs and grass."

Moreover, the petri dish becomes hot as it happens (even though we're talking about ice, which we think of as cold, it's an exothermic reaction), and the "ice" actually feels not hard, but firmly soft, like a gel.

You blew our mind, Petroff, you blew.our.mind.

Here's how they did it?

Says Alex:

"First of all, you need sodium acetate. It is the flavoring that people use to give salt and vinegar chips their taste. Our lab had a convenient jar full of the stuff, so that is what I used (you can buy it online). If you wanted to make your own, it is simple to do. When you mix vinegar (acetic acid) and baking soda (sodium bicarbonate), the sodium and the acetic acid team up to make sodium acetate. The bicarbonate that is left over turns to carbon dioxide and makes all of the bubbles that powered our toy volcanoes.

Now that you have your sodium acetate, you need to get more of it dissolved into the water than the water can hold (i.e., make the water "super saturated"). You can do this by using the convenient fact that when you heat up water it can hold more sodium acetate (and lots of other things) than it can when it's cold or at room temp.

To super saturate the water with sodium acetate, take a jar of water and heat it up close to the boiling temperature. Keep on pouring in sodium acetate until it stops dissolving. Because it stopped dissolving, you know that the hot water is saturated. Because hot water holds more sodium acetate than cold water, as the water cools off it became super saturated. I cooled it off by putting it into the fridge and letting it cool down to about 4C. At this point, we had a dish of water super saturated with sodium acetate. I handed if to Jad and, when he put his finger into it, the the sodium acetate began to form crystals."

Dear listeners, if you try doing this at home, send us some photos/videos, yah?!





More in:

Comments [5]

Miss Moustache from Germany

That.was.awesome. Literally. I feel like the edges of my world/mind just stretched to the size of the universe for a moment. Thanks for that!

Mar. 18 2014 06:03 PM
Travis Smith from North Japan

Ok, I enjoyed this podcast, but you never did actually explain how lakes end up freezing animals instantaneously. In the show, you both seem to come around to the idea that the horse story was bunk...but we know it happens! Heck, the podcast image itself has a frozen fox in a lake. Here are a few more:

So flash freezing by introducing imperfections to supercooled water probably doesn't work on a large scale. Fine. Then how does it happen?

Mar. 18 2014 07:35 AM
Kent from Hawaii

Landscape, people. Always shoot in landscape! Also, where's the toy horse clip? LANDSCAPE!

Mar. 18 2014 01:10 AM
TomCatBklyn from

Great story. Reminded me of a passage from Jules Verne's Off on a Comet, which I read as 11 year-old. I wonder if Verne had heard the same story. In Chapter XXII, Nina throws a small piece of ice into the sea and instantly freezes it solid:

Before the evening of this day closed in, a most important change was effected in the condition of the Gallian Sea by the intervention of human agency. Notwithstanding the increasing cold, the sea, unruffled as it was by a breath of wind, still retained its liquid state. It is an established fact that water, under this condition of absolute stillness, will remain uncongealed at a temperature several degrees below zero, whilst experiment, at the same time, shows that a very slight shock will often be sufficient to convert it into solid ice. It had occurred to Servadac that if some communication could be opened with Gourbi Island, there would be a fine scope for hunting expeditions. Having this ultimate object in view, he assembled his little colony upon a projecting rock at the extremity of the promontory, and having called Nina and Pablo out to him in front, he said: "Now, Nina, do you think you could throw something into the sea?"
"I think I could," replied the child, "but I am sure that Pablo would throw it a great deal further than I can."
"Never mind, you shall try first."
Putting a fragment of ice into Nina's hand, he addressed himself to Pablo:
"Look out, Pablo; you shall see what a nice little fairy Nina is! Throw, Nina, throw, as hard as you can."
Nina balanced the piece of ice two or three times in her hand, and threw it forward with all her strength.
A sudden thrill seemed to vibrate across the motionless waters to the distant horizon, and the Gallian Sea had become a solid sheet of ice!

Mar. 17 2014 08:30 AM
Jim Saling from Seattle, WA

Rock candy is made using a super saturated dolution of sugar in water. A string or a tick is added to the supersaturated solution to stimulate crystal formation. The rock candy is allowed to sit in the solution so that large crystals grow as the water evaporates.

Mar. 15 2014 12:19 AM

Leave a Comment

Email addresses are required but never displayed.

Supported by