Chemistry of common things

Cooking

Doughs

See Doughs, batters, leaveners

Water

On hydration

Coffee's effect on hydration

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

On water poisoning

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

Water poisoning happens when drinking a large amount in a short time, because you dilute (primarily) the balance of salt and other electrolytes.

At some point, this starts affecting cellular function in general, which what we mean when we say water poisoning.

Most of your body contains something like 0.15% salt, and you don't want it to be a lot lower or higher

...except in your blood, which is roughly 0.9% salt. It's higher mainly because it's a big part of regulating the salt levels in your body.

So diluting your blood significantly leads to losing that ability to regulate.

You will probably notice being low in salt as headache, poorer muscle control, and possibly vomiting and diarrhea (possibly your body trying to correct things?(verify)).

The fact that you will feel bad, and have probably associated "I feel bloated, I probably need to stop drinking water" is why most people are at negligible risk. (though if you instead confuse it with "I'm dehydrated, I need to drink water", that's not great)

Time is a significant factor, in part in part because your kidneys are happy to make you pee a lot more

so drinking liters more than you need over a day is much less of an issue than drinking the same amount within an hour

peeing that much wastes some salt in the process, but not very much(verify)

Another part of it is that it takes a while for you to absorb water you drink (basically while it's in your gut) - if there's a lot, there isn't enough time to absorb it.

The time factor is why you see statements like "stay under 3-4 liters of water within in a few hours".

Doesn't distilled water do this a lot quicker?

No.

Sure, tap water and bottled water has things beyond H₂O, including sodium.

When your blood carries something like 0.9% salt (because it's the means of interchange; the rest of your body contains something like 0.15% salt), the difference between 0.003% in tap water and and 0.000% (in theory) in distilled water is two orders of magnitude lower, so the difference is between "almost entirely no salt" and "entirely no salt".

In fancier talk, the osmolality of both is so low that they are almost equally hypotonic, so have roughly the same osmotic effect on your body.

Which is why quickly drinking liters of almost any water based drink will do this, basically because most water based drinks are almost entirely water.

Demineralized and distilled water

Distilled water is (nearly-)pure H₂O, because distillation means you move the water and leave behind most other things.

Demineralized water means few to no minerals

...(unlike fresh natural water, which tends to have minerals in it e.g. due to limestone. Tapwater has more controlled bunch of these things; see also hard water)

...but says little about what else may still be in there

it's useful to keep minerals out of clothes irons (which you want largely to avoid limescale), car batteries (which you want to avoid self-discharge and corrosion), and such.

On contents of demineralized water

Demineralized water often mentions it is not fit for consumption

in practice it's usually pretty clean water, but it's not guaranteed to be pure

largely because depending on the process of demineralization, there may be other things still left in there, say, a few bacteria. Your iron or car battery won't care, but you might

and because it doesn't matter for the intended uses

(also in part because it's also sold in supermarkets, so it's useful, possibly required, to point this out explicitly)

Water hardness

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

Hard water refers to water having relatively high mineral content.

Since we're usually talking about fresh water we want to use as drinking water, this focuses mainly on calcium (also magnesium) as this is a common component that comes naturally from the water passing through limestone, chalk, gypsum, or such. Which gives you things like calcium and magnesium carbonates, bicarbonates, and sulfates.

High is relative - for calcium we're talking talking parts per million, where

soft water is on the order of 30ppm,

hard water on the order of 150ppm.

you get something like 700ppm in a few places

Many other things can qualify for 'mineral content', but typically the amounts are very small, and/or their appearance is local. (e.g. iron, aluminium, manganese)

Salt is one, in that seawater is technically very hard (6000+ ppm) due to its salt, but since it doesn't evaporate, this doesn't apply to fresh water.

Would you prefer soft or hard water?

It's a few different practical considerations, and none of them are hugely important - and the mentioned effects are frequently overstated.

Arguments for softer:

• aesthetic:
  • softer water deposits less scale in showers, drinking glasses, and such
• cost
  • softer water deposits less limescale in washing machines, kettles, which can make them last longer (thick scale makes heating less efficient and in extreme cases causes overheating)
  • soaps lather more, and you need less detergent (or separate water softener) - can be overstated since many contain softeners anyway
  • harder water is less ideal for some industrial processes (and needs fewer additives)
  • with soft water, washing clothes wears the fibers a little less

Arguments for harder:

• softer water will pull out metal out of pipes over time, corroding unlined metal pipes more quickly

(more of a net end effect - there are a handful of other factors on corrosion speed)

which means water infrastructure can be cheaper to run, particularly that infrastructure is currently older, cheaper pipes.

• Harder water could be considered a dietary supplement

though this is frequently overstated. The difference from this switch stays is from 'tiny' to 'small' on your calcium needs, and you need to get your minerals elsewhere anyway.

Arguments for either

• "this water tastes nicer" - you probably prefer what you're used to

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See also:

• https://en.wikipedia.org/wiki/Hard_water

Electrical resistance of water

See Electronics_notes/Resistors#Resistance_of_fluids