> i always thought of water as a pot of rice, of fixed, unchangable, determined molecules

Well you aren't wrong, it all depends on the timescale you are thinking about.

Water molecules are constantly in motion. This is what 1 picosecond of movement in a water droplet at 0 C looks like. They do move around a lot, and a lot of collisions take place in between even diffusion controlled reactions like H-abstraction (timescale 10^(-9) sec).

But relative to molecular vibrations, for instance, they are barely moving at all. Bond stretching vibrations (O-H stretch timescale ~10^(-13) sec), are orders of magnitude faster than collisions. And electronic transitions are several orders of magnitude faster than that (timescale ~10^(-15) sec), so thinking of the atoms and molecules as "fixed" in space would be an excellent picture of them on that timescale. Thinking about an electrical conductor, instead of an H^+ transfer medium, for instance.

Very much so, in that adding a sandbag to one end of the chain ultimately results in a sandbag, albeit a different one, being delivered to the other end of the chain. And unlike a Newton's Cradle (with simultaneous transfers), this is a much less orderly process. Sometimes a sandbag gets passed back before going on, or someone has to wait for a sandbag, etc. This makes it a much slower process than say electrical conductance in a wire.

>I mean, the water molecule is split somewhere

I think you are getting hung up thinking of it as the water molecule. Keep in mind water is a sea of molecules, with a lot of exchanges going on:

H2O ⇌ H^+ + OH^-

OH^- + H2O ⇌ H2O + OH^-

H^+ + H2O ⇌ H3O^+

H3O^+ + H2O ⇌ H2O + H3O^+

So when the hydrogen in a water molecule near the cathode accepts an electron to start forming H2, the remaining OH^- doesn't itself have to migrate to the anode to be oxidized to O2. It just has to exchange with a neighboring water molecule's hydrogen, so now there is a new OH^- a little closer to the anode. So you end up with H^(+)'s being transferred along through the aqueous medium, something like a bucket brigade, to keep supplying H^+ to the cathode and OH^- to the anode, but not necessarily the same H or O in each transfer.

H3O^+ + H2O + H2O + H2O ->

H2O + H3O^+ + H2O + H2O ->

H2O + H2O + H3O^+ + H2O -> -> ->

H2O + H2O + H2O + OH^- ->

H2O + H2O + OH^- + H2O ->

H2O + OH^- + H2O + H2O -> -> ->

In effect you have H^(+)'s being passed along in one direction, and OH^(-)'s being passed along in the other direction.

(Edit: italicized the initial H and O)

Got it. Thanks!

(Edit: But then it screws up mobile.)

Sure! You've basically described fractional crystallization (also called fractional freezing or jacking) as originally used to make Applejack potent.

Just as you can purify a solid by crystallizing it out of solution leaving any contaminants dissolved in the solvent, you can purify a low melting solid by partially freezing it out of a melt, and leaving the contaminants concentrated in the residual liquid. As they are excluded from the solid phase the contaminants get more and more concentrated in the remaining liquid phase, depressing its melting point, so it doesn't all freeze and it can be separated from the crystallizing solid. By repeating the process you can recrystallize the solid and get it purer and purer, like in zone refining silicon to get the high purity required for semiconductor applications.

Or you can turn this around and work with the unfrozen phase, as you are suggesting, getting the dissolved component (the "juice" in your example) more and more concentrated. The classic example of this is actually very close to your idea. It is the original process to concentrate the alcohol in making Applejack: partially freezing fermented cider, removing some water as ice, and repeating the process. The separation isn't 100% so you will never get to pure alcohol: there will always be a little alcohol left with the ice and some water remaining in the liquid phase. (The theoretical limit is 92% pure alcohol). But by going back and forth, thawing and refreezing the "ice" phase to get a little more alcohol out, and adding that to the liquid phase and refreezing that to remove a little more water, they get to 44 proof in Applejack.

I think you mean N2O4, which does indeed have an acrid odor. This is the dimer of NO2, and is in equilibrium with it, such that both species are present:

2 NO2 ⇌ N2O4

This is generally understood to be part of the mixture generically referred to as NOx. But point taken.

Oh, yes. In particular, some refineries blended extra aromatics in with the gasoline to increase the octane: benzene, xylenes, and alkylates. And before catalytic converters and emission standards limited unburnt hydrocarbons in the exhaust, these could give it an almost pleasant odor, especially when it was running rich. (After all, benzene compounds get the name “aromatic” because of the type of odor they have.)

But only if the engine was burning clean and not also burning oil. That made the exhaust smoky. Now days engines are manufactured to closer tolerances and you seldom have to add oil. But back in the day it was routine to check your oil every time you stopped for gas, because there was always a little bit of oil making it past the rings and getting burned in the cylinders.

As you note, a car's gasoline engine converts hydrocarbons and air into CO2 and H2O, both odorless, providing the energy that makes the car go. But there is also nitrogen in the air in the combustion chamber. And although we think of N2 as inert, a small amount does get incorporated into the oxidation chain reaction, to form a mixture of nitrogen oxides, NOx. This, along with unburnt hydrocarbons, lead to smog, so catalytic converters were developed to combat this.

Modern Three-way Catalytic Converters not only convert CO to the less toxic, CO2, and oxidize any remaining hydrocarbons; they also reduce most of the NOx back to N2. But a small amount of NOx gets reduced to ammonia, NH3, as a side product. And NH3 has a noticeable, pungent smell down to 5 parts per million in air.

And although gasoline is primarily composed of hydrocarbons, there are traces of other elements: inhibitors and detergent additives, along with residual sulfur compounds. And whatever sulfur there is, winds up as hydrogen sulfide, H2S, after the catalytic converter. The sulfur level in gasoline should be pretty low now days, below 10 ppm, so this may not sound like much of a problem, but H2S becomes noticeable as a rotten egg smell below 0.1 ppm.

These traces of ammonia and hydrogen sulfide are primarily responsible for the bad smell you notice.

Oh sure! If there were two chlorines present in the chemical, then any fragments in the mass spec that contained 2 chlorines would appear as a triplet of peaks, 2 mass units apart, in the ratio 0.578:0.365:0.058 (if I did the math correctly, 0.76x0.76:2x0.76x0.24:0.24:0.24). So it would be easy to distinguish between fragments with one chlorine or with two chlorines: the characteristic triplet would mean 2 chlorines and the doublet would mean one.

Sure, it's called a Chart of the Nuclides or Table of the Nuclides. Instead of being organized with similar chemical properties in a column, it is organized based on the number of protons and number of neutrons, in columns for one and rows for the other. There are a couple of orientations used. Wikipedia has a Full Table that starts with hydrogen in the upper left, and is oriented using columns for each element (with increasing atomic number going to the right), and rows for each number of neutrons (for the different isotopes of each element) going down.

A full table like this is fine on a wall chart, but it's easier to navigate online. Entering the atomic symbol and isotope mass number in this Chart of the Nuclides, for instance. Entering "Cl" and "35" for chlorine, for example, takes you right to ^(35)Cl. This table uses the other common orientation: with hydrogen in the lower left, increasing atomic number in each row going up, and increasing number of neutrons in each column going to the right. More like a standard X and Y plot.

This layout is convenient for nuclear physicists, in that (among other things) it's easy to relate the starting atom to the result of a nuclear process. Beta decay (loss of an electron), for instance, would transform one of the neutrons in an atom into a proton, increasing the atomic number but not the mass. This corresponds to just moving diagonally up one row and to the left one column in the Chart of the Nuclides: up to ^(35)Ar from ^(35)Cl in our chlorine example. (Not that this is a highly probable event, in the case of ^(35)Cl). And radioactive decay with neutron emission takes you one column to the left in the same row: ^(34)Cl from ^(35)Cl. And Alpha radiation (emission of a helium nucleus, 2 neutrons and 2 protons) is just moving diagonally down 2 rows and left 2 columns: ^(31)P from ^(35)Cl.

But you asked this as a Chemistry question, and although it's periodicity is not related to chemical behavior, it does bring out the role of isotopes in chemistry. For instance, we're used to thinking of the molecular weight of an element as the sum of protons and neutrons. But the molecular weight given for chlorine in the Periodic Table of the Elements, 35.453, is not an integer. So at first this may seem odd. But the chlorine row in the Chart of the Nuclides brings out the fact that elemental chlorine is a mixture of isotopes, mostly ^(35)Cl and ^(37)Cl, with a natural abundance of 76% for ^(35)Cl and 24% for ^(37)Cl. And this averages out to the molecular weight of 35.453 in naturally occurring chlorine.

Another chemical consideration where understanding the isotopes helps, is in interpreting Mass Spectra. When chlorine is present in a chemical being sampled for instance, since 76% of the time the chlorine atom will be ^(35)Cl and 24% of the time it will be ^(37)Cl, this will show up as very characteristic pairs of peaks in a 3:1 ratio, 2 mass units apart in all chlorine containing fragments in the Mass Spectrum. This is a big help in the interpretation of fragmentation patterns.

(Edit: got my directions crossed)

Agree completely with u/velifer and u/floydly. But with that in mind I got very reasonable results when I tried checking up on an old research interest of mine with:

"is semibullvalene homoaromatic?"

Theoretically yes, but you'd have to get twice as much in, and I'm not sure it would permeate into the cherry as easily as alcohol.

Sticking with nontoxic chemicals, several come to mind that could be used to significantly depress the freezing point of water in a bottled drink. Ethanol, of course, but that would affect the flavor and be intoxicating. Sugars dissolve well and will depress the freezing point but will also sweeten the drink, some more than others. Another carbohydrate, glycerin, will sweeten the drink too, but not by as much. And then there's propylene glycol, which is nontoxic, has only a slightly acrid taste, and is sometimes used as an antifreeze in brewing.

These aren't all equally effective. You can compare the wt% concentration necessary to drop the freezing point of water by a given amount, from a table of CONCENTRATIVE PROPERTIES OF AQUEOUS SOLUTIONS. I find, for example, that for a 1° C drop in freezing point it would take about: 2.5% ethanol, 4% propylene glycol, 5% glycerin, 9% D-glucose, or 15% sucrose. (Salt would only take 1.7 wt%.)

So glycerin would be the most effective of the these carbohydrates, and least sweetening. And propylene glycol would be effective with minimal affect on taste.