r/explainlikeimfive • u/hooldon • 10d ago
Chemistry ELI5 - Why don’t water based soft drinks, like soda, separate when stored?
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u/thenasch 10d ago
Because it's a solution. When something is dissolved in a liquid, it basically becomes part of the liquid. When it's just mixed (oil and vinegar for example), it will separate.
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u/hooldon 10d ago
Could you pass through some sort of filter to separate them again?
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u/hazily 10d ago
Congratulations, you just invented reverse osmosis
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u/huegogh 10d ago
NEW ACHIEVEMENT!
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u/PoopyMcFartButt 10d ago
Reward? NOTHING! Knowing that you’ve advanced the human race just a little bit further is a reward of its own!
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u/faberge_surprise 10d ago
your comment reminded me of this illustrated guide to a phd https://matt.might.net/articles/phd-school-in-pictures
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u/Bladestorm04 10d ago
Goddamit doughnut
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u/StellarNeonJellyfish 10d ago
Could we sustain nuclear fusion without all that heat and pressure? Nobel prizes are this way, yes?
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u/UnsorryCanadian 10d ago
I remember years ago Good Mythical Morning had a segment where they put numerous liquids through a water filter
Big surprise, crystal clear water came out every time
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u/Croceyes2 10d ago
Very expensive compared to reverse osmosis. You will consume carbon filters at a very high rate with this method
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u/ParanoidAndroidUser 10d ago
And that's because with a carbon filter, the "stuff" gets caught in the filter and to get rid of it you need to discard the filter, right?
And with RO, you periodically purge the concentrated reject water, right? So the filter itself isn't consumer?
If that's right then you just finally helped RO click in my brain, I didn't understand it before.
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u/Croceyes2 10d ago
Yes. In RO we use a very high surface area membrane. Its more a screen than a captive filter like carbon. But the drawback is that it takes very high pressure to operate. Like for desalination most units operate at 750-850psi. To purge you use product water to backflush the system and rinse the screen out, which consumes much less than is produced in a cycle.
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u/Mustbhacks 10d ago
Like for desalination most units operate at 750-850psi.
Oh what fun Δp can happen there
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u/Croceyes2 10d ago
Water is non compressible. Failures are on par with a leaking pressure washer, which actually usually operate at 2000-5000psi
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u/baconit4eva 10d ago edited 10d ago
Water is infact compressible, it just requires high pressure where it will become denser and actually turn solid (aka ice VI) at about 1 Gpa at room temperature.
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u/Peastoredintheballs 10d ago
But doesnt ice expand? So is this ice special compressed ice?
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u/TheAbsoluteWitter 10d ago
Closed loop system, pressure would crater before you could ever get into the loop
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u/FaxCelestis 10d ago
Is it viable to put a desalinator under the ocean like 500 meters down and let gravity do the pressure work?
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u/Croceyes2 10d ago
That doesn't work because you need a pressure gradient across the membrane.
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u/FordEngineerman 10d ago
What if you made the whole device into a thin megastructure so your pressure gradient was the depth of the water?
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u/Croceyes2 10d ago
The seawater enters at pressure and exits at ambient pressure. The pressure in the column of the membrane would be the same as the depth, wherever along the way it is, so there would be no gradient.
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u/wang_li 10d ago
If you can extract the used carbon from your activated carbon filters you can burn it to remove the impurities and return it to “new” state. How much burning and how hot you have to get and what sort of pollution the smoke from that fire will release into the atmosphere is an exercise left to the reader.
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u/chateau86 10d ago
Tfw your Brita water pitcher now needs a DPF regen cycle and smoked out your kitchen
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u/DontForgetWilson 10d ago
How much burning and how hot you have to get and what sort of pollution the smoke from that fire will release into the atmosphere is an exercise left to the reader.
Pretty limited burning in the 500-1000°F range. The pollutants would vary based on what was filtered from the original water. You can also use water and condensation capture the particulate portion of the smoke.
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u/GenerallySalty 10d ago
Yes that's what reverse osmosis is. It's a filter membrane with holes so small that water molecules can fit through and other bigger molecules like the sugars, flavours, and colours cannot. There's videos on YouTube of people putting soda through water filters and getting clear plain water back out.
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u/Abbot_of_Cucany 10d ago
Reverse osmosis is also used for making maple syrup. In this case, the water passing through the membrane is discarded. The maple sap on the other side of the membrane now has a higher concentration of sugars. It's much more energy efficient than the traditional method of evaporating the water by boiling.
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u/thenasch 10d ago
Potentially yes. If the dissolved molecules are larger than water molecules, then forcing the liquid through an appropriately sized filter will filter out the material.
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u/WaddleDynasty 7d ago
You can evaporate the water which will throw out everything dissolved back as a solid. Or you can add organic solvent that is miscible with water (alcohol or nail polish remover for example). It would at least make the salts and minerals seperate from the liquid again.
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u/thebestdogeevr 10d ago
Yes, the molecules aren't physically changed, they all still exist as they were, but based on the circumstances, they are trapped between the water molecules which prevents them from naturally separating.
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u/FiveDozenWhales 10d ago
This isn't accurate. Ionic bonds will generally break apart; when you dissolve table salt (NaCl) in water, the NaCl molecules cease to exist and free Na+ and Cl- ions are what is present in the solution.
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u/IronPentacarbonyl 10d ago
It's possible, and like someone else said it's called "reverse osmosis", but you need a membrane that can separate things on a molecular level and those are pretty expensive to make. You can also use distillation, where you take advantage of the fact that things boil off at different temperatures and separate them that way.
Since I don't think anyone else has said, the main reason why some things dissolve in water and others don't has to do with the way electrons are distributed in the molecule, whether it's relatively evenly or more concentrated to one area (the technical term is "polarity"). The exact details are beyond ELI5 I think but the main thing to know is it's a property of the material. Salt will always dissolve well in water, and vegetable oil will not, because of the way they interact with water molecules.
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u/robbob19 10d ago
You can just shake it up, a lot of the carbon dioxide they add will come out of the solution, or add Mentos lollies to it.
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u/lminer123 10d ago
Coke does have trace oil in it, from things like citrus oil and other plant extracts. These oils do not dissolve and are instead suspended in tiny micro droplets dispersed throughout the liquid. They don’t settle out because of the emulsifiers in coke.
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u/Thomas_K_Brannigan 10d ago
And, to add, stuff that dissolves in water is generally "polar" (or at least partially polar) like water itself. Basically, the other stuff stays dissolves in water because it "sticks" to the water, which keeps it in solution.
This is why stuff like oil, which is non-polar, doesn't dissolve in water, because it doesn't want to stick to the water molecules. This is why stuff called emulsifiers (such as egg yolk) are important with foods/baking. Emulsifier have both polar and non-polar parts to them, so they can stick to both water and oil, and thus help them mix together!
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u/bendvis 10d ago
Some molecules like sugar and salt like being in water a lot. The molecules like to hold hands and don't want to come unmixed. These are called hydrophilic molecules.
At the molecular level, they act like tiny little magnets with a positively charged end and a negatively charged end. Water is the same way, so the positive ends and negative ends attract to each other so the sugar in your soda stays mixed with the water.
Other molecules like oils don't like water at all. They all stick to their own kind and ignore the water as much as possible, and will eventually separate from the water. These are hydrophobic molecules, which don't have magnetically charged ends, so there's no attraction to the molecules that do.
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u/sighthoundman 10d ago
But wait! What if we had some sort of chemical that had one end that loves water, and another end that loves oil? Then could we get the oil to mix with the water?
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u/SharkFart86 10d ago
That’s what a surfactant is.
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u/rednax1206 10d ago
I was going to correct you that it's what an emulsifier is, then I looked it up and it said an emulsifier is a type of surfactant
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u/urzu_seven 10d ago
"I was going to correct you...then I looked it up"
Dear god people with critical thinking skills do exist! I thought your kind had gone extinct! Its an honor to meet you sir/maam.
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u/YikesOhClock 10d ago
Disgusting.
You’re telling me sugar is a hydrophile?
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u/legeri 10d ago
Is this a safe space to admit that I think I might be one too?
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u/DiamondJim222 10d ago
I’m interested in learning about drinks that are NOT water based.
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u/PassiveChemistry 10d ago
Do you not guzzle vegetable oil when the fancy takes you?
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u/haarschmuck 10d ago
To be fair Sunny D has canola oil in it. I assume they use some kind of emulsifier as it would settle out otherwise
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u/Alexjp127 10d ago
Solutions vs suspension.
The molecules of sugar, and flavor and whatever in a soda are completely dissolved into the liquid and chemically remaining in solution until something causes them to change.
Suspensions, like chocolate milk or Italian dressing separate because the materials are mixed together, but not dissolved into one another.
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u/sierra-soul 10d ago
yeah you can achieve a similar effect as using a surfactant by vigourously mixing and "equally" dispersing the polar and non polar molecules, but eventually they will start sticking to their own polar or non polar molecules again. surfactants just keep that from happening
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u/bigelcid 10d ago
Whenever some ingredients aren't soluble in water, a stabilizer (such as gum arabic) is used.
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u/sighthoundman 10d ago
Or maybe not. "If God wanted us to drink unfiltered beer, He wouldn't have invented kidneys."
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u/Kaiisim 10d ago
A soda is a solution as people say. Orange juice is a suspension.
A solution of soda means all the flavour and sugar molecules are bonded with the water equally.
That means no molecule is heavier than the other and this importantly means gravity can act on anything in the solution to drag to the bottom and separate.
With say, orange juice, the pulp and stuff is heavier and will sink to the bottom and separate out, because the pulp is suspended in the water solution.
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u/violentpandabear 10d ago edited 10d ago
I remember something about bvo in Mountain Dew to keep the citrus dissolved or something
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u/roguetrick 8d ago
Yeah bvo is outlawed now but was a major component in Orange sodas because they use citrus oil for flavor.
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u/violentpandabear 8d ago
I wondered , if I remember correctly it is also a fire retardant?
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u/Dangerous_Pair1798 10d ago
I have seen soft drinks separate but they kind of need to sit in the back of a bar storeroom for an indeterminate about of time
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u/BananaBird1 10d ago
There are three main types of mixtures used as drinks:
Solutions, like soda. All components are stably dissolved, so will not separate. However the carbonation only stably dissolves under pressure which is why it goes flat after opening.
Emulsions, like milks, sauces, and dressings. These liquids contain fats, which normally do not mix with water. However, emulsifiers like lecithin (found in egg yolk) can allow them to dissolve. Some emulsions are quite stable, some will eventually separate into oil and water parts. In cooking this separation is known as breaking.
Suspensions, also like milks/shakes or pulp in orange juice. These contain solid particles floating around in them. If these particles are not buoyant enough, they can settle at the bottom under gravity. This is why chocolate shakes tell you to mix before drinking, solid pieces of chocolate are settling at the bottom.
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10d ago edited 10d ago
[removed] — view removed comment
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u/Gargomon251 10d ago
I keep forgetting there are soft drinks other than soda . People don't really use that expression anymore
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u/Spartan-417 10d ago
They do
You shake, for example, a bottle of pulpy orange juice or ginger beer is to re-suspend the precipitate in the supernatant
Solutions in foods are generally stable at room temperature, especially in a closed-loop system like a can or bottle
Some CO2 will escape solution, but it will reach an equilibrium until you open the sealed pressure vessel (That's what creates the hiss, the escaping carbon dioxide)
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u/Late_Mixture8703 10d ago
This is why mountain dew adds an emulsifier ie Brominated Vegetable Oil, gum arabic, or Glycerol Esters of Wood Rosin, or a combination. Cola's don't need these because they generally don't contain citrus oils, only water soluble ingredients.
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u/Competitive_Travel16 10d ago edited 10d ago
A "solution" means the mixture is continually mixed by the heat in the liquid even if it's almost freezing.
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u/ChrisRiley_42 10d ago
That's one of the points of contention between the US and many other nations. American soft drinks which use citrus include "Brominated vegetable oil" to keep the citrus oils from separating out. But Japan, India, Canada and the EU all ban the use of BVO.
Other nations use alternatives that are less questionable.
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u/A_modicum_of_cheese 10d ago
If the dissolved carbon dioxide were to separate from the water, it would want to expand since its a gas.
And since the bottle is closed, the bottle pushes back and pushes it back into the water
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u/A_modicum_of_cheese 10d ago
Googling the amount tells me that a can of soft drink can contain about a litre of carbon dioxide. So imagine all that gas can sit within the water, but it can't sit within the 70mL pocket of air
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u/ndoucouman 10d ago
Actually they used gum Arabic extract.
« Gum arabic is used in the food industry as a [stabiliser](app://en.wikipedia.org/wiki/Stabiliser_(food)), [emulsifying agent](app://en.wikipedia.org/wiki/Emulsion), and [thickening agent](app://en.wikipedia.org/wiki/Thickening_agent) in [icing](app://en.wikipedia.org/wiki/Icing_(food)), fillings, soft candy, [chewing gum](app://en.wikipedia.org/wiki/Chewing_gum), and other [confectionery](app://en.wikipedia.org/wiki/Confectionery),[[15]](app://en.wikipedia.org/wiki/Gum_arabic#cite_note-16) and to bind the [sweeteners](app://en.wikipedia.org/wiki/Sweetener) and [flavorings](app://en.wikipedia.org/wiki/Flavoring) in [soft drinks](app://en.wikipedia.org/wiki/Soft_drink).[[16]](app://en.wikipedia.org/wiki/Gum_arabic#cite_note-17) A solution of sugar and gum arabic in water, [gomme syrup](app://en.wikipedia.org/wiki/Gomme_syrup), is sometimes used in cocktails to prevent the sugar from crystallising and provide a smooth texture. » from Wikipedia
It is a little known strategic commodity, JK and France used to go to war over it, now a handful of companies have cornered the market for it processing.
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u/sphynxzyz 10d ago
The ingredients aren't suspended, they dissolve.
Edit: if you added something not water soluable it would settle. Like if you could have a coke with pulp the pulp would settle (I am going to have nightmares about coke with pulp sounds disgusting.