Difference between revisions of "Chemistry of common things"

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==On filtering water==
 
==On filtering water==
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===Activated carbon===
 
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'''What is activated carbon?'''
 
'''What is activated carbon?'''
  
Basically, charcoal with more surface area (porosity, if you will) than average charcoal, by burning it hotter.
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Chemically it's regular carbon/charcoal, but with more surface area (porosity, if you will) than average charcoal,  
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made by burning it hotter and producing granules with more cracks and pores.
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That surface area is why it's more reactive for the same mass of charcoal.
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That surface area is why it's more reactive for the same volume of charcoal.
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'Reactive' is somewhat misleading - the process is adsorption, which is more a 'stuck on its surface' than a 'has reacted chemically'.
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Though carbon ''does'' act as a catalyst for some contaminants.
  
  
  
Does an activated carbon filter work?
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'''Does an activated carbon filter work?'''
  
Yes.
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Does it take some stuff out of water? Yes.
  
  
What does it remove?
 
  
In aquarium water, it will (by mass) largely react with ammonia and nitrates (poop)
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'''What does it remove?'''
In drinking water, it can help remove chlorides (if your local water company leaves noticeable amounts - not all do)
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It will etract a lot of other things too.
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In aquarium water, it will (by mass) largely react with ammonia and nitrates (fish poop)
There is a common point that you should not put AC in food, or perhaps even a filter,
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In drinking water,
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: it can help remove chlorides (if your local water company leaves noticeable amounts - not all do)
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: also things like some some [https://en.wikipedia.org/wiki/Volatile_organic_compound organic compounds], some cleaners, some solvents, hydrogen sulfide, pesticides
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: ...but not e.g. the calcium that makes water hard.
  
activated carbon can ''be'' medication, mostly absorbing ingested poison fairly immediately after ingesion.
 
  
(regular carbon is less effective, though )
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It will extract a lot of other things too.
  
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There is a common point that you should not put AC in food, or perhaps even a filter,
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in that it can lessen the effect of medication
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(though it can also ''be'' medication, e.g. absorbing ingested poison fairly immediately after ingestion)
  
  
but if you ingest AC, it can also easily absorb
 
  
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'''How long does activated carbon last?'''
  
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If primarily adsorbing things from passing water, this depends largely on how much there is to adsorb.
  
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If it's also compressed tightly enough to also act as a filter for small particles,
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it might clog up before it's done adsorbing.
  
How long does activated carbon last?
 
  
On paper, months.  
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In aquariums, there is more to remove, and people tend to replace it every three weeks or so.
  
But, say, aquarium people are taught maybe three weeks
 
  
Or, when water is dirty, maybe after a week.
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Around drinking water, used on already-fairly-clean drinking water,
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it could easily last months or, if not used much, even years.
  
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Or shorter if your water is e.g. very cholride-ey.
  
  
  
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'''What is reactivated carbon?'''
  
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Basically it means making activated carbon from used activated carbon,
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rather than from a raw source like e.g. coconut shells, coal, or peat.
  
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Because it's not reacted, most adsorbed things are relatively easy to remove,
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and heat (again) is one of them.
  
  

Revision as of 17:10, 6 August 2022


Cooking

Doughs

See Doughs, batters, leaveners

Greenery

Trees, O2, CO2

Water

On hydration

Drinking slowly?

3 liters a day, or less?

Coffee

Alcohol

On water poisoning

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Water poisoning happens when drinking a large amount in a short time, because of what it does to certain balances in your body, primarily salt and other electrolytes.


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

(your blood is 0.9% salt, because it's a big part of regulating salt levels)


Water poisoning refers to managing to dilute your body significantly, because that starts affecting cellular function in general, which is the real problem.

In the more immediate sense, dilute your blood significantly leads to this, because your body can't regulate it anymore.


You will probably notice this poor function because it leads to 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 confuse it with "I'm dehydrated, I need to drink water", that's not great)



Time is a significant factor that tends to make people safe

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 doing so within an hour
peeing that much wastes some salt in the process, but not very much(verify)
in part because because it takes a while for you to absorb water you drink, basically while it's in your gut
(related to why moderately fast rehydration in hospitals is done via saline IVs - in seveeral ways it's more practical than drinking as that relies on timing and attention(verify)).

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.

Quickly drinking liters of almost any water based drink will do this, basically because most water based drinks are almost entirely water.


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

Yet the concentrations of these (called its osmolality) are very low (order of roughly 0.003%(verify), so they matter more to the taste of the water and maybe being a mild supplement (these amounts are very low relative to the amounts we need - in particular for salt it's the salt we add to our food that keeps that balance).

The point is that both the maybe 0.003% in tap water and and 0.000% in distilled water are both are so much lower (one or two orders of magnitude) that they are both hypotonic, and have roughly the same osmotic effect on your body.




On bottled water

On filtering water

Activated carbon

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)


Does distilled or demineralized water lead to nutritional deficiency?

Water hardness

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

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, we are typically focusing on calcium (also magnesium) which comes naturally from the water source 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:

Fluoride in drinking water

Salty water

Greywater

Electrical resistance of water

See Electronics_notes/Resistors#Resistance_of_fluids

Oxyhydrogen