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What drives this? EILI(NOT)5
Metals are quite weird in this regard.
An important point to make early is that metals don’t bond the same way normal molecules do. Water, for example, bonds with itself in liquid and solid form with hydrogen bonds. This is where an electronegative oxygen can bond with the positive hydrogen. It’s extra strong because the oxygen is quite negatively charged and the hydrogen quite positively charged due to electro negativity differences.
Metals bond entirely differently, and it’s complicated. They form what you’ve probably heard of as a sea of electrons. Metals are generally just atoms, not molecules (though interestingly gallium actually forms Ga2 molecules). But this sea of electrons is basically where all the electrons in a particular shell of the metal atom kind of blend together into one massive superstructure of electrons. It’s very quantum mechanical and can almost be thought of as a single macroscopic object made of trillions of electrons.
This sea is what allows metals to conduct electricity effectively, but it also holds the atoms together.
When a metal is solid, all the atoms do not move relative to one another, the atom next door stays the atom next door. It forms a lattice.
In order to melt a metal, you only need to disrupt the lattice structure, which is not held together too tightly. Whereas to boil a metal, you need to disrupt that sea of electrons. It’s important to note that a melted metal still has that sea of electrons in tact, melting it does not disrupt that. Boiling it does though, it rips the atoms apart destroying the sea. But that takes a lot of energy.
This is still simplified, there’s a lot of quantum mechanics going on
So liquid metals still conduct well? You'd need like tungsten wires to test it
Yes. Mercury was used as a switch back in the day. You would fill an ampule half way with it, and put two unconnected wires at one end. Then depending on how the ampule was tilted, the Mercury would slosh to the side with the wires and connect them.
Pretty sure mercury switches are still a thing in certain industries.
They were still using them in Lethal Weapon 1.
Merc Stuff, real advanced shit.
At least as advanced as the 1950s era thermostat in my parents' house.
I love you for this reference, used in this context.
hah, that's a cool switch
My thermostat still uses this contraption. It's very old.
i had fun turning the AC on as a kid by flicking the mercury bulb and never actually turning the AC to "ON"
Was just reading about these on Reddit a couple days ago. Apparently they were silent too. The only reason we don't still have them is because they made a law to get rid of unnecessary uses of mercury to limit exposure.
That’s not the only reason, although it is good enough on its own. Mercury switches are usually disposed improperly and leak Mercury to the environment, especially in consumer products.
Mercury switches are also notorious for their electrodes decaying over time due to the intense heat generated when the switch opens or closes.
They’re also limited to situations needing low cycle rates. The droplet of Mercury has to physically move back and forth to create a cycle, and due to the mass/intertia of the droplet this strongly limits the cycle rate.
They’re generally fragile and require extra cost in protection or replacement.
They only work in certain orientations, as they depend on gravity. Flip the device on its side and the switch no longer works. Move the device too vigorously and the switch may activate on its own.
They can’t be scaled to extremely large or extremely small sizes.
It is all true, with a caveat that this applies specifically to the switches where the contact is made by a rolling ball of mercury, like the tilt switches used in the thermostats and similar.
Curiously, there are also other types of mercury switches and relays, similar to their ordinary mechanical counterparts but in which the contacts are additionally coated with liquid mercury. Until 1960s these switches were the the fastest way to turn the electric current on, and were the gold standard for the very high speed electronic test equipment.
They were really common in thermostats until I think the '90s. I remember seeing them in the one in the house I grew up in and thinking they were neat.
Also extremely dangerous and potentially unreliable. AFAIK, up until WWII they were used in many explosives ordnance but due to a high failure rate were phased out ushering in better alternatives.
Very safe and reliable in most cases, just not the best idea as a trigger on a bomb
Thanks, that re-words it much better.
Yeah, I replaced an old thermostat in my house many years ago, and took it apart and salvaged the mercury switch from it. I've kept it just because it's cool looking.
Yeah, i also remember reading somewhere that the older electric bells were made with a mecury container as it's switch.
To clarify: "back in the day".
About 10 years ago I replaced my home thermostat which effectively had a mercury switch with a nice digital one with precise controls.
You can still buy those for thermostats in countries without product safety regulations
This is in part how household thermostats worked, I think. I know mercury was involved - when I removed a very old one from a house it was a real pain to get rid of safely.
Gallium is in the same group as aluminum (aluminium?) and in Romania we call those semi-metals due to not being in the main metals group yet showing at least some metallic properties. Quite quirky stuff honestly. First two columns as well as the 3-12 ones (Iron is in that range) would be the classic proper metals.
Question, if you know: Why semi-metals are a thing?
This is true for pretty much all the periodic table, but we like to organize things into categories that really don’t exist. We like to think of it as ionic bonds, covalent bonds, metallic bonds, etc. but the truth is that it’s a continuum, and some elements are in weird spots where they are right at the boundary of what we think of as two different groups.
These things will have bonds that have both metallic and covalent character, or might act metallic in certain conditions and non-metallic in others.
Gallium for example, covalent bonds with itself to make Ga2, but then those Ga2 can metallic bond with other Ga2. So it’s a bit of an in between
I mean the noble gases category is pretty good and does have clearly distinguished properties: they don’t form chemical bonds unless in extreme (or for the heavier ones, somewhat extreme) conditions. But I guess for everything else….. yeah.
What’s the difference between the lattice structure of metals and crystals? Are crystalline forms not a result of a lattice-like molecular structure?
They are both the result of a lattice like molecular structure. The difference between them is the types of bonds involved. There can be hydrogen bonds, ionic bonds, metallic bonds, and more.
But solid metal is definitely considered a crystal, just like quartz or table salt. There are other non-crystal solids too, but metals form crystals. But again, just because two things are crystals, doesn’t necessarily mean the bonds holding the atoms, ions, or molecules together in the lattice are the same. And they can all have varying degrees by which they resist melting and boiling.
Thanks for the insight, so is there a difference between what type of bond is formed by something like a lump of iron or a gold nugget vs a grown metal crystal like bismuth?
Well when we compare bond type between different metals, they are slightly different. Different atoms, like iron or gold, have different electronic structure (which orbitals are occupied by electrons, which influences how they interact with each other.) But they do all have similar broad stroke properties, though not exactly the same.
As for a lump of iron or a lump of gold vs a bismuth crystal, the key here is that a bismuth crystal will be completely regular and repeating across its whole mass. Every atom (with some defects, of course), will be in one big crystal lattice.
Lumps of metal on the other hand, are built a bit differently. They’ll have small regions that are perfectly lattice-like, but they have many of these different crystals sitting next to each other. For example, imagine a cubic lattice which is where the atoms sit at the corners of a cube. Table salt does this. A lump of metal will have a small region where they do that, but then there will also be another lattice, maybe tilted at 45 degrees from the first. And you’ll have many of these mini crystals which are all in random orientations. They’re all stuck together in a lump, but they aren’t one big crystal.
Your bismuth crystal would have that, one big crystal.
You could make gold, iron, or any single crystal you like. But it’s oftentimes difficult. A classic example is in computer chips they need these massive (relatively speaking) silicon crystals with no or minimal imperfections. Different elements will be more or less easy to achieve this. Bismuth is an easy one, but some require very advanced techniques like vapor deposition, to ensure everything is lined up nicely.
Well this has all been amazingly informative thanks a bunch
They are the same, metal lattice structures can be called crystalline as well. What you would think of as a crystal would be quartz which is silicon - not a metal. But metals form a similar lattice structure, of which there's 12 forms I believe. They are physically the same but metals have a much stronger bonding force which is why steel is stronger than quartz.
Im not the same guy, but i think a lattice is more of a lining up of atoms, whereas a crystalline structure forms from a location and grows outwards, which can cause intersections between other crystalline structures randomly.
This should be added to text books.
They have really strong bonds to other molecules (in a pure metals case, atoms) in the fluid
Think of a bowl of ice cream, and a glass of water
frozen ice cream and frozen water are both frozen, but at room temperature ice cream becomes a goopy mess while the water just remains water. Just because you can melt an ice cube in your hand doesn’t mean you could boil it in your hand.
Now the ice cream and the water had different changes to their composition during that temperature change but after that they still boil at basically the same temperature.
Now instead of ice cream and water, think different metals. They may have different states at different room temperature but the heat actually needed to boil it is still very high compared to room temperature.
I mean there's 100 degrees between water melting and boiling.... it will melt in the palm of your hand too.
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Liquid phases are kind of weird.
If you look at a phase diagram, say for water, there's a triple point where it can be solid, liquid, and gas at the same time. That's at one exact temperature.
Below that pressure, it can't be liquid at all, no matter what you do.
Above that pressure, the temperature range for the liquid phase gradually increases. So the difference between the melting and boiling points of a particular substance can be anything from zero to a lot, depending on the pressure.
And then when the pressure hits the critical point, you can't tell the difference between liquid and gas anymore, and the whole question stops making sense.
If you look at a phase diagram, say for water, there's a triple point where it can be solid, liquid, and gas at the same time. That's at one exact temperature.
Wait, what? Is there any photo/video of such a phenomenon?
Wow, I had no idea that was possible. So I guess the pressure is the key to make water boil at 0.1C?
All melting/boiling points are determined by both temperature and pressure, we always just assume atmospheric pressure when we talk about boiling points and metling points and stuff. in fact, this is how a pressure cooker works, it can cook food hotter by introducing pressure which raises the boiling point of water. also a vacuum freeze dryer works the opposite, it pulls a strong vacuum which causes ice to sublime directly to vapor instead of melting. if you've ever looked at food packaging and it has special instructions for "high elevation cooking" that's because once you get to high enough of an elevation, the atmospheric pressure is actually low enough to where you have to cook things differently.
you can see all these properties visually by looking at what's called the "phase diagram" which shows you whether something will be a liquid, solid, or gas at any given combination of temp and pressure
If you compare the one for water
https://www.chemistrylearner.com/phase-diagram-of-water.html
To something else like CO2
https://www.chemistrylearner.com/co2-phase-diagram.html
One very important difference you'll notice is that the slope of the solid/liquid line for water angles to the left, while just about everything else angles to the right. This is a unique property of water where its liquid form is more dense than its solid form (ice floats in water). If you add pressure to a liquid it generally will form a solid but if you look at water, as you increase pressure it actually goes the other way and turns the solid in to a liquid.
So I am not a chemistry major by any means (more of a physics guy than anything)
With "dry ice", which is AFAIK solid CO2 that sublimates when exposed to room-temperature air, does that work at basically any temperature since the liquid form doesn't appear until 5.11atm which is more than 5 times the pressure of normal sea level?
Yep, exactly. If you look at that phase diagram and draw a horizontal line at 1atm that'll show you how CO2 behaves at atmospheric pressure. since there's no solid->liquid phase change in that region, you'll only get sublimation (solid->gas)
Yes, I don't remember the phase diagram for water, but by playing with the temp and pressure you can get materials in phases that you'd not get at room temp/atmospheric pressure.
This is the coolest thing I've seen in awhile.
Do the ice chunks at the start look like a penis to anyone else?
Isn’t pressure the reason why the earth’s oceans could never fully flash boil off?
Well I mean there's a lot of reasons. It depends what exactly you're asking.
The entire ocean can't evaporate under current conditions because there's a lot of water in the air already, so the chances of a water molecule leaving the ocean through evaporation are roughly the same as the chances a water molecule in the air will add itself to the ocean. So that's a pressure argument. It also requires enough gravity to keep all that water vapor somewhere near the ocean.
And then there's the water in the air that decides to add itself to a raindrop over land that eventually gets back to the ocean. Kind of a pressure argument, indirectly, because it still relies on condensation.
And then there's the ridiculous amount of energy it takes to heat or boil water, compared to other things.
Meteor impacting the earth and flash boiling the oceans. Depicted in movies mostly.
That'd get a good chunk, sure, but it wouldn't fully flashboil the entire ocean.
If it did, I’m not sure there would be much Earth left at all.
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Imagine the gallium as tiny tiny metal balls, how they interact depends on how much energy or heat is added to the balls; your hand adds this heat when you hold it. You can imagine heat as the balls vibrating, they vibrate more with more heat. When the gallium is solid there isn't enough heat for the balls to move place each other so they form shapes called a lattice. Once enough heat is added some of the balls can start move around each other and leave the lattice, this is melting.
As the balls start to break the lattice all the heat/energy that is added is used to break the lattice, the balls don't vibrate more, if you're holding it in your hand you'll notice it warms up then stays the same temperature when it starts to melt until it's a liquid.
Once the lattice is broken it's like taking the balls and putting them in a bin, even though they're all solid balls they still move like water. For something to boil the balls need enough energy to fly out of the container, it takes many times more energy to fly away then it does to break the lattice
That's a good explanation for melting and evaporating, but it doesn't actually answer the question of why gallium has such a large liquid temperature range.
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Yeah but gallium’s boiling point is about 2,400°C which is waayy more than 100°C
Tungsten melts at 3422 C and boils at 5930, which is a similar relative difference as gallium, just hotter.
It is not at all clear what your point is. Gallium doesn't boil at 100 C, it boils at 2403 C, so why would you say they're the "same"? Is the sameness to you just that the boiling point is higher than the melting point? Because, yeah, obviously.
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For the same reason that you can melt water by holding it but you cant boil water by holding it. Easy to melt doesn't mean easy to boil, its just coincidence that galliums melting point is within the range of comfortable human temps
ice melts in your hand, why does it boil at 212F?
melting points and boiling points are different properties.
That's great. It's a very good example. It didn't come in my mind.
There's no rule for how far the melting and boiling point of an element can be.
Every material has different properties. Explaining why it is different would be way above eli5.
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Yeah but gallium’s boiling point is about 2,400°C which is waayy more than 100°C
Think of it like stretching a strong elastic band just a little bit, compared to ripping the elastic band apart. Stretching the bonds between metal atoms allows them to "relax" and move around each other, but they're still quite close together and strongly bonded together. Boiling a metal requires ripping those bonds apart entirely, and that takes a lot more energy.
Same reason ice will melt in your hand but the water it becomes doesn't boil.
Melting and boiling points are different temperatures on everything.
No different to ice really.
Can easily melt in your hand - but you're in a bit of trouble if somehow it's boiling in your hand!!
Melting is changing from a solid to a liquid and boiling is changing from a liquid to a gas. I think it seems like you think these two things have to be close together, but they don’t. Water for example, melts at 0°C and boils at 100°C, a pretty big difference though not as big as gallium. It has to do with the structure and how hard it is for heat to make the molecules move fast enough to turn into gas. Metals also boil at a higher temp in general
Boiling point for many materials is very very far from the melting one; it’s much easier to add a tiny bit of energy needed to loosen the bonds between atoms/molecules, than to actually detach those atoms/molecules completely from the liquid.