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Seven surprising things about ice that we learnt from science comedians Matt Parker, Helen Arney and Steve Mould © Getty Images

Seven surprising things about ice that we learnt from science comedians Matt Parker, Helen Arney and Steve Mould

Published: 16th November, 2020 at 19:55
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In a recent episode of the Science Focus Podcast, the Spoken Nerds went deep into the nitty-gritty all about ice.

In a recent episode of the Science Focus Podcast, we talked to the three 'Spoken Nerds': Matt Parker, Helen Arney and Steve Mould. They are the hosts of the Podcast Of Unnecessary Detail, and in each episode, they choose a single word and dive into the nitty-gritty of everything around the topic.


For this special episode, we brought you a raft of unnecessary details about ice. We’ve dug out the best bits of the conversation to share with you. Or, listen to the full episode below.


There are two types of instant coffee: the horrible kind, and the really horrible kind

Steve Mould: This is this is a bit of unnecessary detail for when you've got an awkward silence around the coffee machine – when you eventually get back to the office.

There's actually two types of instant coffee. There's the horrible kind and the really horrible kind. The horrible kind is the freeze dried stuff. Freeze drying is an amazing process. You've probably had a freeze dried coffee, you get freeze dried fruit as well: if you buy a fancy cereal, that's the fruit in there.

To freeze dry, you take a raspberry, for example. You put it in a box, you seal the box and you lower the temperature to minus 40 degrees centigrade. You've frozen the fruit, so you've got ice in there. And then crucially, you suck all the air out of the box. You lower the pressure.

Ice does this weird thing at very low pressures. If you bring the temperature back up again to room temperature, instead of melting, it turns directly into a gas. So it skips the liquid phase completely. The solid ice turns directly into a gas. It's called sublimation.

And what that does is it leaves holes behind where the ice was. So, the structure of the raspberry or the strawberry or whatever it is, remains. If you pick a bit of a fruit out of your fancy cereal, it's really light and fluffy because it's full of tiny pockets of air.

So, freeze dried coffee is really porous. So it's really instant. When you add the hot water, it gets into all those pores and it dissolves really, really quickly.

The really horrible kind of coffee is the spray dry stuff. When you spray dry coffee, that's like the traditional way of drying something. You do it with heat. So you get this coffee, you spray into a hot box and all the water evaporates.

The problem with doing it that way is, with all that heat there, some of those aromatic molecules will escape the coffee. Those aromatic molecules give coffee its flavour, so when you spray dry coffee, you're removing a lot of the flavour, whereas when you freeze dried coffee, you're only removing the water. Those flavour molecules remain in the coffee.

And you can tell if you if you go into a shop, the expensive coffee, if you look at the actual granules, that is like brown chips, whereas the sprayed dry stuff, these horrible dark clumps of powder, and they're also much cheaper. That's how you can tell the difference.

More things we've learned from the Science Focus Podcast:


Freeze drying is a 500-year-old innovation

SM: It's an amazing innovation in terms of coffee and actually wasn't invented by coffeemakers. It was invented, like a lot of things, in a military context in World War Two. It was used as a way to preserve blood serum.

Actually, that's a reinvention. It was used by the Incas in the 15th Century. They would hike their crops up a mountain, and because it's colder up there and the pressure is lower, their crops would freeze dry. So the method has actually been around for ages.

Matt Parker: I would say, on behalf of the the hipster fancy coffee drinkers of the world –

SM: Are you in that group?

MP: I am. I'm on the fringe, but I'm definitely in. In fact, while we're recording, I'm drinking coffee that I use my hand grinder to grind up the roasted beans, single source etc.

So, hipster coffee drinkers would never go near freeze dried coffee. However, if you told them it was hand carried up a mountain and left to freeze dry by some traditional tribe... that is the only way you'll sell freeze dried instant coffee to hipsters.


Snowflakes with eight-fold symmetry make Matt Parker really cross

MP: I've been running a campaign for many, many years against inaccurate snowflakes.

We're recording this as we are coming out of summer, straight into autumn. And winter is not far away.

People get upset when they see the first Christmas decorations going up. I get upset when I see the first 'snowfake' going up, which is some kind of decorative snowflake which doesn't have six points.

All snowflakes have six-fold symmetry there. They're hexagonal or they got pointy bits, but they're always six-fold. Whereas if you go out in the world and you look at shopfronts or BBC Two got this wrong a couple years ago with their Christmas decorations. I don't think Science Focus Magazine has ever fallen afoul of this. But you'll see eight-pointed snowflakes everywhere. You just cannot have an eight pointed snowflake. So I started the hashtag 'snowfake'.


But snowflakes should be pentagonal

MP: So everyone says, look, water, when it freezes, gives you a hexagonal structure because of the shape of a water molecule. Picture it from like classic science diagrams – you might remember from school that water looks like a little boomerang for little kind of little angled top half of a triangle, let's say.

We would say, mathematically, it has the tetrahedral angle. The oxygen in the middle has four pairs of electrons, two of which have a hydrogen, and the other two are just electrons on their own. We can't see the other two, we only see the two with hydrogens. By 'see' I'm talking about in diagrams or the structure of the molecule.

So it forms the angles, in other words, in the centre of a tetrahedron because it's four equally spaced points. But the hydrogen behaves a bit differently to just the electrons by themselves, in terms of how far away they are from the nucleus. It's actually slightly distorted. The angle between the two hydrogens is not the tetrahedral (109 and a half degrees), but in water, it's 104 and a half degrees.

Everyone says, okay, well, you got a bunch of those and they form a hexagon. But the internal angle of a hexagon is 120 degrees. Whereas the internal angle of a Pentagon is 108 degrees, which is much, much closer. And so actually water, if it's free to crystallise however it fancies, will form pentagonal rings – because that is much, much closer to the angle in a water molecule.

SM: So why does it happen?

MP: It's only because of the way it then stacks into a lattice. If you want to have something repeating and nice and neat, then it gets forced into a hexagonal structure.

So the hexagonal shape you see in a snowflake is not strictly because of the shape of the water molecule like we're always told, it's because of the arrangement of lots of water molecules. But that arrangement changes depending on the pressure and the temperatures. Like Steve was saying, if you cool ice down, you change the pressure. Weird things starts to happen to it. And several steps later: instant coffee.


Bees are smarter than scientists, they just don’t have the publications to prove it

MP: Six-fold symmetry is great in a lot of things we want to pack things together well. So that's why bees' honeycomb is a hexagonal cross-section. There's actually something called the honeycomb conjecture: that hexagons are the best possible shape if you want to pack them together really well, but minimise the amount of edges you need for the space inside.

But that wasn't proven to definitely be the best mathematical arrangement until 1999. So actually, the whole snowflake thing goes back to Kevlar, who wrote about why snowflakes are hexagons in 1611, but only very recently have we got a proper understanding of why it forms in that particular arrangement. So it's been a question for humans for a long time, but only recently have we thought to crack the maths and the chemistry behind it.

Helen Arney: Matt, is this only because bees haven't been able to write scientific papers?

MP: I maintain the honeycomb conjecture is the record for longest time between discovery and proof mathematical result. Because bees cracked it, what? Millions of years ago. How old are bees? I don't know. That's biology.

But then it took millions of years before a different organism proved that bees had it right all along.


If on a winter’s night you dropped a Canadian tree frog, it wouldn’t bounce

HA: When Canadian tree frogs in the winter reach temperatures of minus 10 or minus 15 degrees, their skin freezes. So, if you drop a Canadian wood frog in the winter, it doesn't bounce. It clunks, because it has an antifreeze that it produces inside its bloodstream.

The antifreeze proteins cause the blood to freeze, it actually encourages the blood to freeze. So it actually sucks the water out of the cells, and then the frog's liver produces all of this sugar and glucose, which then packs into the cells. So the result is a frog where the blood is frozen, but the cells are full of sugar and dehydrated. And that's how it survives.

MP: So a frog can be freeze dried, and then, when it thaws out, it's alive? And if it's anything like coffee, it's also going to taste terrible.

HA: But it would taste better than if it was spray dried.

MP: Good point. Good point.

HA: That's how it survives. It kind of uses its blood to try to make sure that the blood gets frozen. And that sucks the water out of the cells so the cells don't burst because they're not full of ice. They're full of sugar rather than water ice.

MP: I want to take back my previous statement, because if the cells are now full of sugars, it might taste better.


Philosophers might be right to bet on cryonic freezing

HA: There is one use for antifreeze proteins that is still being worked on, but potentially could be amazing. And that is with organ preservation.

So with a donated organ, you have to get it to the recipient within a few hours and keep it around zero degrees centigrade. Otherwise, it starts to break down. But there's a possibility that antifreeze proteins could be used to not only extend the life of donated organs, but also be used for storing tissue.

At the moment if you're storing like frozen tissue for a future use, you need to stuff it full of stuff that isn't brilliant and is quite toxic. So, potentially, antifreeze proteins could be used because they're less toxic. They have lower concentrations to get the same effect.


Can you see where I'm going with this? Cryogenic freezing may be possible. So, if you choose cryonic freezing as your future (I don't necessarily recommend it), then you may be stuffed with fish proteins instead of antifreeze. It's a possibility.


Amy BarrettEditorial Assistant, BBC Science Focus

Amy is the Editorial Assistant at BBC Science Focus. Her BA degree specialised in science publishing and she has been working as a journalist since graduating in 2018. In 2020, Amy was named Editorial Assistant of the Year by the British Society of Magazine Editors. She looks after all things books, culture and media. Her interests range from natural history and wildlife, to women in STEM and accessibility tech.


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