day update and recipe

[jinian]

Got last Friday's chem quiz back. It is disappointing, to say the least. I know how to write net ionic equations. It's just that the part where people know what happens in the reaction when given only the products still appears to have a largish magical component, from my point of view. baratron? Anyone? How do you know that, given HBr + Na2CO3, you get NaBr, CO2, and H2O? (Rather than, oh, let's say hypothetically H2CO3, which may or may not exist but does seem like a fairly reasonable-looking compound.)

Was amply distracted from my injuries by going to Dilettante with rysmiel and then to two Twice Solds Taleses. My virtue in bookshop-guiding was rewarded -- I found a certain out-of-print book I've been especially looking for as a present.

I decided to make a spicy lentil soup for dinner, since my cold doesn't seem to be just a cold any more; hot, spicy things were needed to chisel loose the gunk in my throat. Also, it was cold enough today to make any kind of stew sound wonderful. When I diced the purple potatoes we happened to have, I thought they looked like they had built-in iodine, like when we stained the leucoplasts in the potato in last quarter's botany class. I wonder if that's the sort of thing that's going on, or if people have just bred them to have chromoplasts in foolish places because it's cute. Probably the latter.

Anyway, between those and the carrots and the spinach, I decided to call this recipe "Secondary Lentils." (Yes, I probably should be smacked. Sorry.)

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Ingredients:

a bit less than 1/4 cup olive oil

• about half an onion, even if you don't like it alone (like me)


• half a dozen cloves of garlic, maybe more


• assorted spices:
  cayenne pepper, turmeric, cinnamon, cumin, cardamom, (garam masala if it's already mixed,) black pepper,
  --
  rosemary, bay leaf, some Apiaceae seeds that might be fennel or something but they smell like they'll work, a bit of salt


• 3 medium carrots


• a knob of ginger


• two cups lentils (green ones are very good, brown are fine too)


• water, about eight cups total


• one big potato


• a bunch of spinach


• one tbsp. red wine vinegar




Directions:


Chop the alliums. Heat the oil in a large pot over medium-low heat and put into it more of the spices before the "-- " than you think you want. Turn the heat up a bit and add the alliums. When they're just a bit brown at the edges, add the carrots and ginger, and cook until those are soft, which is not all that long.

Add the lentils and stir them into the vegetable-spice-oil mix. (Kitchen superstition says doing this before adding water is a good way to distribute flavors, but I've never tested it scientifically.) Add some water and the spices appearing after the "-- ". The water thing is kind of up to you; I like the soup to be thick, so I add as little as I can get away with. If you don't care and the pot will take it, pour on all eight cups at once.

Cook that, stirring occasionally, for 45 minutes, or until the lentils are soft enough to eat comfortably. Add diced potato and give it another ten minutes or so, then stir in the chopped spinach, add the vinegar (not too much or it turns the whole thing weirdly fruity), and turn off the heat.

Like lots of soups, this is better the next day.

Celery and tomatoes can go into it, too, if you like. It's forgiving stuff for the most part.
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I seem to be getting really sick. Wim says I'm feverish, whee. My brain certainly hasn't been working all day, and my throat is burning up. Doctor tomorrow.

Comments

[marzipan-pig.livejournal.com]

I wish I remembered my chemistry better. could it be that some of those are more stable than others and you just have to kind of memorize the more common molecule possibilities? or could it be something with atomic number (is that the rightt word?)? or that the smaller possibiliteis are more stable? I always relaly liked working out that part but now the details of HOW to do it are eluding me too.

[technocracygirl.livejournal.com]

One of the best things to do, especially if you've got HBr, HCl, HF, NH4, etc, is make water. After that, see if there's any simple stuff (salts, CO2, NH3, etc.) that you can make. And memorize those polyatomic ions (PO4, SO3, etc.) because they *won't* break apart.

[jinian.livejournal.com]

Thanks. It's just that I was under the impression that the carbonate ion was also unlikely to break apart. I can remember to try for water first.

*sigh* I really wish this class were being taught in a way that made sense to me. I'd prefer principles to five million examples and things to memorize, and it's not always that principles are impossible because I've gleaned some from he does say. At least someone else is teaching chem 150 next quarter.

[marzipan-pig.livejournal.com]

my college chem classes (even organic, which is very unusual to be taught that way) was taught principle based and while it was a lot easier than memorization for most students, some people had a lot of trouble. it was also a lot harder for standardized tests (esp organic) where you tended to have less time and were supposed to just churn out answers instead of thinking about why (people who were taking chem tests tended to have memorization fests right before tests).

a good teacher can do a ltitle of both to hit both styles of learning and generating answers but sometimes good teachers are little miracles, aren't they? :)

(nice icon)

[elynne.livejournal.com]

Urgh, sick Kylee != good. :( Get better! NOW!! [kidding] [mostly]

[baratron.livejournal.com]

Hopefully this will make things seem less like magic...?

LOVELY INORGANIC EQUATIONS:

Combustion:
metal + oxygen --> basic oxide
non-metal + oxygen --> acidic oxide

Neutralisation:
acid + base --> salt + water (Neutralisation)

Exceptions:
acid + carbonate --> salt + carbon dioxide + water
acid + ammonia --> ammonium salt only


acidic oxide + alkali --> salt + water
(As you’d expect from the Lewis theory (if you’ve done that yet). This is still neutralisation!)

ammonium salt + metal hydroxide --> ammonia + water
(I think writing “metal hydroxide” here is tautology, as the only non-metal hydroxide I can think of is water, but I might be forgetting something.)


Reactive metals:
(Those above hydrogen in the reactivity series. For most purposes, these are (in order):
potassium, sodium, calcium, magnesium, aluminium, zinc, iron, tin & lead.
Note that carbon comes between aluminium and zinc in the reactivity series. Metals below carbon can be extracted from their ores by roasting the ore with carbon present.)

reactive metal + acid --> salt + hydrogen

reactive metal + water --> metal oxide + hydrogen
Note that for very reactive metals (K to Ca), the oxide that’s formed will then react with water to form a hydroxide. This reaction happens so quickly that you cannot isolate the oxide in solution.


Does that help?

H2CO3 does exist - it's carbonic acid, a very weak acid which is very poorly dissociated (split into ions). When carbon dioxide is bubbled into soft drinks to make them fizzy (or carbonated), a very small amount of the carbon dioxide dissolves in the drink to form carbonic acid. (The rest just sits in the top of the can as CO2 gas). This is why fizzy drinks often taste slightly acidic or "tangy". In the atmosphere, carbon dioxide dissolves in rain and makes it slightly acidic (this is a natural process, not really due to pollution, so not to be confused with acid rain) - which isn't generally a problem except when it comes into contact with limestone (calcium carbonate). Limestone's used a lot in buildings because it looks nice, but carbonic acid reacts with it, eroding it over time. But this is a big digression. The point is: it's possible that when your acid reacts with a carbonate, a small amount of carbonic acid does form. However, because the acid has such a small dissociation constant, it is far more covalent than ionic in character, and so it behaves more like an organic acid than an inorganic one. Thus the reaction is unlike normal inorganic neutralisation and you end up with CO2 gas.

I wouldn't have given any of that last paragraph to kids, btw. I'm telling you because you're clever and interested :)

[baratron.livejournal.com]

Eeep! Sorry, brain fart in the middle there.
ammonium salt + metal hydroxide --> ammonia + water
should read
ammonium salt + metal hydroxide --> ammonia + metal salt + water

(e.g. NH4Cl + NaOH --> NH3 (g) + NaCl + H2O)

[jinian.livejournal.com]

It is good to have smart friends. Thank you for the explanation, and for the compliment too. :) Things usually hang together better in my head the more related information I've got, so this really helps.

[mathochist.livejournal.com]

Wow, I'm impressed.

All I remembered was that things had to combine such that the outer electron shells were full. Why some such combinations seem to happen and others don't, though, was the question.

throwing information at the wall

[eub.livejournal.com]

Also, caves! Limestone caves, with limestone stalactites, same process.

Semi-related: they protect limestone structures from sulfuric acid rain by applying a layer of barium carbonate. Calcium sulfate is slightly soluble, more than the original carbonate, so it washes away to expose further stone, but barium sulfate is less soluble. Why that is I don't know.

Soft-drink detail: rather a lot of carbon dioxide dissolves in the water -- almost one volume of gas per volume of water at room temperature and pressure, and more under pressure -- but only a percent or two (I'm seeing varying numbers) of that lives on the carbonic-acid side of the equilibrium.

[baratron.livejournal.com]

It would probably be impressive if I didn't have a degree in chemistry and wasn't training to become a high school science teacher? ;)