The Let's Play Archive

SpaceChem (2013 Tournament)

by Wild M

Part 31: Closed Tournament - Round 1 - The Chem

The Chem in SpaceChem, Closed Tournament Round 1

3 Omega Acids

Well, this unobtainium stuff obviously doesn’t really exist. But let’s look at the molecules these exotic things are based on. The acids are similar to propanoic acid, ethanoic (acetic) acid and methanoic (formic) acid, but a big difference is the triple bonds between the omegas, making it hard to break up these molecules.

Anyway, formic acid is an important component of ant venom and nettle stings. It’s used as a preservative in livestock feed and for leather tanning. It’s quite corrosive but not very toxic.

The somewhat bigger acetic acid is the main component of vinegar (besides water). It has a distinctive sour taste and smell. It’s used a lot as a food additive. Other than that, it is a precursor for polyvinyl acetate, a polymer used in paints and glues. It’s used in the production of cellulose acetate, which is one of the possible compounds for photographic film base. It won’t combust like old nitrate film, but it will degrade over time, releasing acetic acid. If your old film rolls start smelling like vinegar it might be time to make a back-up.

Propanoic acid has yet another C, giving it some more fatty acid properties. Like the smaller organic acids, it’s used as a food preservative. Other than that, it’s used for polymer production, and for propanoate esters, which tend to have fruity odors.

Speaking of fatty acids, this puzzle’s title reminds me of ‘omega-3 fatty acids’. Of course, those have nothing to do with the omega element. It’s just an unofficial way of naming certain unsaturated fatty acids. ‘Omega-3 fatty acids’ has become a sort of buzzword in the food industry. They are similar to vitamins in that small amounts are required in your food, but there’s no definite proof at all that additional supplements are required or even healthy. There is some indication that those supplements may cause long-term negative effects to your health, though.

Our product is similar to cyclobutane, a somewhat strained molecule. C-bond angles don’t like to be at 90°, instead they tend to be at 109°, the furthest 4 lines coming from one point can be apart in three-dimensional space. Each bond points to one corner of a tetrahedron, if the C-atom is in the center. This is not the case with cyclobutane, making the molecule strained and a bit less stable compared to molecules with larger rings. Cyclobutane derivates occur in biology and have some specific uses. Wikipedia notes carboplatin as an anti-cancer drug. By the way, when cyclobutanes are linked together, the shape resembles a ladder. Linked cyclobutane molecules are officially named ‘ladderanes’.


Getting Bronzed

Dihydroxyacetone or DHA has a formula of C3H6O3 (some H’s were left out in the structure in the puzzle). This means it could theoretically be built from some carbons and exactly three whole water molecules. Compounds like that are known as carbohydrates or more simply as ‘sugars’. During research on using DHA as a medicine, doctors found that if it was spilled on the skin it would cause a tanning effect. This happens due to a reaction of DHA with amino acids in the outer layer of the skin similar to the Maillard reaction which causes the crust of bread and meat to turn brown when they are baked.

While things aren’t fully certain (like usual in science) it seems that in general DHA tanning is safer than sunbathing. One reason is that DHA only reacts with the dead outer layer of the skin and can’t damage any deeper parts. However, pure DHA can cause the skin to turn orange-ish, so modern spray tans usually combine it with other stuff.

Bronze is an alloy, consisting mostly of copper. Modern bronze usually has 88% copper, 12% tin. There’s also alloys called ‘commercial bronze’ and ‘architectural bronze’, but those mostly consist of copper and zinc, which means they are actually brass alloys. Anyway, bronze is hard, strong, and does not corrode easily. In the Bronze Age, before even stronger steel was invented, ‘bronze’ was used for sea ship parts, musical instruments and bells, statues, and so on. Ancient bronze was usually made out of copper and whatever scrap metal they could find, so the composition varied quite a bit.

In modern times... bronze is actually mainly used for similar purposes. Some things just stay the same.



Rust, or iron(III) oxide. It occurs in nature as the mineral hematite and was first formed when organisms started releasing oxygen into the atmosphere, which reacted with the iron. Common rust is actually a mixture of iron(III) oxide and some iron(III) oxide hydrates, which contain water. The color of these different oxides varies from black-brown to red. Different from copper oxide and aluminium oxide, rust does not form an airtight surface layer, so iron under a rusted surface will keep rusting. There are several ways to slow this down. One that I like is called cathodic protection. You attach a block of metal that is oxidized more easily (e.g. zinc) to the iron object. While the zinc oxidizes, electrons will flow from the zinc to the iron, reducing any iron oxide on the surface back to iron metal. The sacrificial metal zinc has to be replaced by a new piece every so often.

Naturally occurring alumina is mainly used to make aluminium metal. It’s also used as an abrasive, for instance on sandpaper. It’s much cheaper than diamond and has a 9 on the Mohs scale of mineral hardness (diamond is the highest with a 10, but the scale is not linear at all.) As a pure mineral, it’s known as corundrum, and it is transparent and colorless. However, something very interesting happens when tiny amounts of impurities are added. Add the tiniest bit of chromium and you get a shiny stone called a ruby. Add some titanium and iron and you get a blue sapphire.

Gallium(III) oxide’s chemistry is similar to that of alumina. However, it’s mainly used in technologies such as semiconductors, lasers, nanotech and also for catalysis. While Ga2O3 can be made in several crystal structures, it does not occur in nature. Instead, gallium is found as an impurity in certain other minerals.

I talked about iron already in the previous update.

Aluminium is a very common element in the Earth’s crust and the most commonly used metal after iron and iron alloys. It is quite reactive but usually forms a very thin impenetrable oxide layer on the outside, protecting itself. It’s very light, making it essential for modern airplane construction. This time lapse clip shows why you aren’t allowed to bring mercury on an airplane: it forms an amalgam that quickly spreads, weakening the structure.

By the way, the metal is called aluminium with 2 i’s and anyone who says otherwise is wrong.

I like gallium and I’d like to have a sample for myself, but unfortunately it’s a bit expensive. Gallium is a metal that melts at 30 °C, 86 °F. Different from the liquid metal mercury, it isn’t (really) toxic. You can buy a gallium spoon kit in some practical joke shops. Give the spoon to someone with a cup of tea and it will melt when they try to stir. Nice to play around with. Some gallium alloys such as ‘Galinstan’ (Ga, In, Sn) have an even lower melting point, below freezing of water. As it isn’t toxic and it isn’t nearly as reactive as another low-melting sodium-potassium alloy, this has some practical uses. Other than that, gallium is mostly used in semiconductors and in LEDs and lasers.



I’m going to start with the pure halogens this time. Remember from the last episode how chlorine is a yellow-green corrosive gas, while bromine is a slightly less corrosive red-brown liquid? Well, as we go down the halogen group, after chlorine and bromine we find iodine. Iodine is a blackish solid at room temperature, which sublimates into a purple gas. It’s still a reactive halogen, but not nearly as dangerous to handle as chlorine or bromine.

Astatine is the next halogen. It is quite radioactive. The most stable isotope only has a half-life of 8.1 hours. We don’t know much about its physical properties, because when you try to purify a sufficient amount of elemental astatine, its own radiation heat will cause it to vaporize and react immediately. Looking at the halogen trend it’s likely that at room temperature, astatine would be a black solid, or it might have a metallic appearance and act like a metalloid.

Now, interhalogen compounds such as the reactants in this puzzle, tend to have properties that lie between those of its two elements. Both astatine monoiodide and astatine monobromide seem to exist. As astatine is such an unstable element, they won’t exist for long, so they don’t have any uses other than satisfying some scientific curiosity.

‘Bromine monoiodide’ exists but is called iodine monobromide, as bromine is the more electronegative element. As expected, its properties are between bromine and iodine. It’s a dark red solid with a melting point of only 42 °C, 108 °F.


Vinegar distillation

I talked about all these compounds already. So instead here’s an additional note on so-called ‘glacial acetic acid’.

Glacial acetic acid is the common name for pure acetic acid without water. It’s called ‘glacial’ because it freezes at 17 °C, 62 °F, forming crystals that look somewhat similar to water ice. Apparently, it wasn’t until the late 18th century before chemists found out that glacial acetic acid is just undiluted acetic acid.

Glacial acetic acid shouldn’t be confused with acetic anhydride, which is what you get if you take two acetic acid molecules, and combine them in a chemical reaction that releases a water molecule. It has very different properties and different chemistry. While it has a number of industrial uses, acetic anhydride is a restricted material in some countries because it’s needed for the production of heroin.

By the way, it’s not very efficient to distillate acetic acid solution to get glacial acetic acid, because the boiling point of acetic acid (118 °C, 244 °F) is close to that of water. The common way to solve this is something that seems related to Feinne’s explanation on azeotropes. They add a compound such as ethyl acetate to the mix. Ethyl acetate forms an azeotrope with water which boils at 70 °C, 158 °F. Distill this mixture, and you will boil off an azeotropic ethyl acetate/water mixture and leave behind glacial acetic acid.


Molecular Key Carving

Copper is a quite stable metal, that is known for its good electrical conductivity. Silver is even better at that, but way more expensive. Copper is often used in alloys, such as bronze, brass and cupronickel. Many coins, including American and European ones, are made of several copper alloys. For instance, American ‘nickels’ are actually made of cupronickel (75% Cu, 25% Ni). Copper is mostly used in electrical application, but it’s also been used a lot in architecture (think of copper roofs and church spires).



Ethyl nitrite is a volatile compound which can be prepared from ethanol. The Wikipedia page only says that it’s used in South Africa as a remedy for colds. They say it may have Dutch roots, as Amish people in the USA used it as well. It’s also known as ‘sweet spirit of nitre’ because of its fruity odor. Well, I’m Dutch and I have never heard of this stuff, so if does have Dutch roots we have forgotten about it. Maybe that’s for the best, as I’m not sure how safe it is.
It is related to the class of compounds that are sold as the recreational drug known as ‘poppers’ (used as an aphrodisiac). It seems to have a vasodilation (blood vessel widening) effect and in larger concentrations it’s explosive. I know another compound with those two properties: nitroglycerin. That’s not a coincidence. As I said before, molecules in which a large percentage of the mass is taken up by nitrogen tend to be volatile. And coincidentally, nitrites cause vasodilation. In the human body, nitroglycerin forms nitrites as well.

Glycine is the smallest amino acid, a building block of proteins in all life forms on Earth. The NH2 is the amino group, the COOH is the acid group. Glycine occurs as a so-called zwitterion. The COOH loses an H+ while the NH2 gains one. The end result is a ‘molecule’ with one positive charge and one negative charge. So the whole thing is neutral again.
Glycine also has some commercial uses. It is used as a sweetener in food and as a buffering agent in cosmetics. A buffering agent is a substance that makes it easier to keep the acidity of a solution stable. In 2009, NASA found glycine in a comet sample, which gives some credit to the hypothesis that the molecules of life can be found everywhere in the universe.



I can’t find much on butanediperoxoic acid. I’m not sure it’s stable, the two peroxides might make it explosive. There are some articles floating around about the molecule with a long C-chain attached to one of the inner C’s. Apparently, it’s a strong oxidizer and can be used as a bleaching agent. That’s not surprising, it’s similar to what hydrogen peroxide does.

Tartaric acid is a common molecule in many plants. It is an anti-oxidant and used as a food additive for that purpose. In a very large dose it acts as a muscle toxin, but it takes like half a kilogram of the stuff to kill an adult human. Anyway, tartaric acid is a chiral molecule: it has different stereoisomers. This acid was used in the discovery of stereochemistry molecules, which polarize light in different ways. There are three forms, of which two show optical activity[1]. However, when those two are in a 1:1 mixture, they cancel each other’s polarization. This mixture was originally called ‘racemic acid’ (Latin: racemus, ‘a bunch of grapes’, which is a fruit in which tartaric acid occurs). Nowadays, the word ‘racemic’ refers to any 1:1 mixture of optically active molecules.

[1] Check the Wikipedia page for structures.