The Let's Play Archive

SpaceChem (2013 Tournament)

by Wild M

Part 34: Closed Tournament - Round 2 - The Chem

The Chem in SpaceChem, Closed Tournament Round 2

Alpha finals: Tetrazine Isomers
Input molecules: Nitrogen, Hydrogen
Output molecules: Cyclotetrazene, Chain Tetrazene, Fork Tetrazene

Net reaction: 2N2 + 2H2 --> N4H4

I discussed hydrogen back in Round 6. I don’t seem to have discussed nitrogen yet.

Nitrogen, N2
Melting point: -210 °C, -346 °F
Boiling point: -196 °C, -320 °F
Molecular mass: 28.01u
Density: 1.25 g/L

Nitrogen is a common and stable gas. It makes up 78% of the atmosphere. Early chemists ‘discovered’ it as part of the air that does not support combustion or life. The N2 molecule has a very strong triple bond. The bond needs to be broken to use the nitrogen atoms for other compounds such as amino acids.

In nature, nitrogen is ‘fixed’ in more useful compounds by lightning and by a certain genus of bacteria called Rhizobium. These bacteria live in ‘nodules’ in the roots of legume plants. That’s why farmers sometimes grow clover (a type of legume) on a field for a year. It works like a natural fertilizer.

All the energy required to break the triple bond and fix nitrogen is released when a compound decomposes to elemental nitrogen. Additionally, a gas takes up a lot more volume than a liquid or a solid. That’s why so many nitrogen compounds are violently explosive.

Nitrogen is useful in the lab as an inert gas. If some reaction can’t be exposed to oxygen or water vapour, just keep pumping dry nitrogen gas into the reaction vessel. Liquid nitrogen, abbreviated by engineers as ‘LN2’, is often used as a refrigerant. It’s relatively cheap and can be stored and transported easily in Dewar flasks. It’s used medically for removing warts by freezing them off (that’s about as pleasant as it sounds) and to store and preserve blood and cell samples. The most obvious danger of liquid nitrogen is frostbite, which can be prevented by not touching the stuff. Another danger of LN2 is that it will replace oxygen when it’s stored in a badly ventilated room, which can lead to suffocation.

Tetrazene, N4H4
Melting point: none, decomposes.
Molecular mass: 60.06u
Density: 1.74 kg/L (predicted)

The ‘common’ form of tetrazene is the compound called ‘chain tetrazene’ in the puzzle, either with the double bond between N1 and N2 or between N2 and N3 (according to Wikipedia, they tautomerize, that is, the double bond switches places by itself).

‘Chain tetrazene’ is an energetic compound that rapidly decomposes at 90 °C, 194 °F. It will also explode due to friction, impact or sudden heat. It can be synthesized from hydrazines.

There is a more complicated compound with the trivial name of ‘tetrazene’ or ‘tetrazene explosive’. The compound contains a tetrazene group but is different in that it has an actual use in primary explosive compositions.

‘Cyclotetrazene’ seems to have an official name of tetrazetidine. It doesn’t matter much, because either it doesn’t exist at all or it’s an even more explosive isomer of the ‘chain tetrazene’. Apparently, in 2012 they actually managed to synthesize a stable compound containing the tetrazetidine group for the first time [1].
By the way, one of the few things that a Google search for cyclotetrazene turns up is some discussions elsewhere about Leylite’s puzzle.

‘Fork tetrazene’ is actually named 2-aminotriazane. The only thing I can find about it is an old official nomenclature document where they give it as an example of an exception to a naming rule. It doesn't seem to really exist.

Feasibility of the reaction
Feasibility: low.
It’s hard enough as it is to ‘break down’ nitrogen gas. Turning it in an explosive in a single step? Not gonna happen in any way that you could survive.

Reaction energy: Endothermic, 300 – 600 kJ/mol (calculated)
Hmm, that’s quite energetic but we’ve seen bigger numbers. If I had to guess, I’d say that’s because the nitrogen-nitrogen bonds don’t have to be completely broken.


Beta finals: A Glass of Water
Input molecules: Rubidium Hydroxide, Cesium Hydroxide, Hydrogen Hydroxide Water
Output molecules: Water

Net reaction: Depends on how efficiently you use the nuclear reactors, I guess.

Of course I talked about water already. Let’s take a look at the others.

Rubidium Hydroxide
Melting point: 301 °C, 574 °F
Boiling point: 1390 °C, 2534 °F
Molecular mass: 102.48u
Density: 3.20 kg/L

Rubidium is an alkali metal, just like sodium. We can expect rubidium hydroxide to have similar chemical properties as sodium hydroxide (lye). And it does. Rubidium hydroxide is a strong base. However, as we get down the list of alkali hydroxides, they get more and more corrosive. Rubidium hydroxide reacts very similarly to sodium hydroxide and potassium hydroxide, but is more dangerous to handle. It requires protective clothing and face protection. RbOH reactions tend to be very exothermic, so they should be done slowly and with caution. Rubidium is less common than sodium, so RbOH is also more expensive. Hence, RbOH isn’t used much. It’s sometimes used in research and it’s an intermediate in the production of many other rubidium compounds, but that’s about it.

Like the other alkali hydroxides, rubidium hydroxide can be prepared by simply putting rubidium oxide (which occurs in some minerals) or rubidium metal in water. In the latter case, hydrogen gas is formed, which will combust because of the reaction heat.

Cesium Hydroxide
Melting point: 272 °C, 545 °F There’s several different melting points listed online but this one seems correct.
Boiling point: Unknown.
Molecular mass: 149.91u
Density: 3.68 kg/L

The next alkali hydroxide down the list is this one. As expected, it’s even more reactive than RbOH. Wikipedia notes it can corrode through glass rather easily. As RbOH (or KOH) can almost always replace CsOH in reactions and is ‘safer’, CsOH sees even less use. However, it seems it’s used as an electrolyte in alkaline batteries in freezing environments. By the way, it seems the ‘official’ IUPAC name of the element is ‘caesium’ but I’ve never seen anyone use that spelling outside the UK. CsOH can be formed in the same way as RbOH, by reacting Cs or CsO2 with water.

Here you can see what the reaction of the two metals with water looks like:

At 1m55s they put rubidium in water, next they use cesium. Hydroxide solution and hydrogen gas are formed.
By the way, you might have seen the ‘alkali metals in water’ clip from the television show ‘Brainiac’ where they blow up a bathtub. Just so you know, that was completely faked. They actually used dynamite or something.

Feasibility of the reaction
Feasibility: low.
Well, transporting the water input to the output is easy enough, but as I said before, nuclear reactions like this aren’t really feasible in any case.

The reaction energy depends on the net reaction(s). It’s simple to calculate, though. Just take the mass of all reactants, take the mass of all products (including waste), and calculate the mass difference. Put that through E=mc2 to get the reaction energy. I’ll leave the actual calculation as an exercise for the reader.


Psi finals: Conversion Factors
Input molecules: ‘S-Triazine?’
Output molecules:, S-Triazine

Net reaction: Ω3Σ3H3 --> C3N3H3

Well, let’s skip compounds of nonexistent elements and go right to S-Triazine.

Melting point: 81 °C, 178 °F
Boiling point: 114 °C, 237 °F
Molecular mass: 81.08u
Density: 1.38 kg/L

Triazine looks like a benzene with 3 carbons replaced by nitrogens. There are three triazines: 1,2,3-triazine (N’s next to each other), 1,2,4-triazine and 1,3,5-triazine, which is what we have here. 1,3,5-triazine is also known as s-triazine. Triazines are aromatic compounds (just like benzene) and can do some benzene-like reactions. However, they can also be considered a trimer of hydrogen cyanide (HCN). In certain organic reactions, it can replace HCN and is considered a safer alternative, as triazine is a solid while HCN is a gas at room temperature [2]. Like HCN, s-triazine is poisonous.

A common derivative of s-triazine is melamine (2,4,6-triamino-1,3,5-triazine). Melamine has many uses. In combination with formaldehyde it forms ‘melamine resin’, a strong hard plastic used for kitchenware. It is also used as a fire-retardant additive in paints and other plastics.

Hey, that’s strange, didn’t I say that nitrogen compounds like to go boom? That’s true for many compounds, but not all of them. Melamine doesn’t explode, but when it’s heated it will decompose to form nitrogen gas. Nitrogen gas displaces oxygen, stopping other combustion reactions.

Melamine doesn’t have (much) acute toxicity, but it does have chronic effects such as causing kidney stones and increasing the risk of bladder cancer. You might’ve heard of the (mostly Chinese) melamine scandals, where the stuff was added to milk powder. They did this because standard protein content tests react to the nitrogen in melamine, making the protein content appear higher than the actual value. This led to infant deaths and criminal prosecution in China and stricter control mechanisms and rules all over the world.

Feasibility of the reaction
Nonexistent elements, skipping this.


Omega finals: Barium Shortage
Input molecules: Iron(III)oxide, Urea, Polyethylene
Output molecules: Barium Sulfate

Net reaction: More nuclear stuff

I talked about iron(III) oxide, the main component of rust, in my first Closed Tournament update. All other compounds are new.

Melting point: 134 °C, 273 °F
Boiling point: None, decomposes.
Molecular mass: 60.06u
Density: 1.32 kg/L

Urea, also known as carbamide, is an interesting little molecule. In humans and many other animals, it is mostly a waste product formed from metabolism of amino acids. Urea is named after urine. Another common waste product from the metabolism of nitrogen compounds is ammonia, NH3. Ammonia is much more toxic than urea, and in our bodies ammonia is quickly converted into urea even though that takes energy. Urea, which is neither basic nor acidic, is a way to safely store ammonia until we can dispose of it.
Fish and other aquatic animals are basically surrounded by an obvious way to dilute ammonia to non-toxic levels, so their nitrogen metabolism do not include (much) urea at all.

Urea is commonly used as a fertilizer. Soil bacteria can turn it back into ammonia which is turned into nitrogen compounds used by plants. There are many other commercial uses, a whole list of them can be found on Wikipedia. Some of the more interesting ones are as an ingredient in skin creams and moisturizers and in tooth whitening products. Actually, some ancient cultures and also a few modern folks use urine directly for these purposes…

Urea was first discovered as one of the compounds in urine in the 18th century. In 1828, a German chemist named Wöhler managed to synthesize urea from silver cyanate and ammonium chloride, two inorganic compounds. This was the first time an organic compound was made without involvement of living organisms. The experiment discredited the ‘vitalism’ theory, which said that compounds of living organisms are fundamentally different from inorganic compounds and contained some kind of ‘life force’. Wöhler’s discovery made him a pioneer in the field of organic chemistry.

Melting point: 100 – 130 °C, 210 – 270 °F
Boiling point: Unknown/decomposes.
Molecular mass: 200000 – millions u
Density: 0.910 – 0.940 kg/L (LDPE); 0.940 – 0.965 kg/L (HDPE)

That info table looks unusual, doesn’t it? That’s because we’re talking about a polymer here. Polyethylene is what you get when you combine a whole lot of ethylene molecules, breaking the double bonds, so each C has an additional place to bind to another C. By repeating this process, you get single molecules with macroscopic lengths, made from many thousands of ethylene monomers.

PE is the most common plastic, but its actual properties differ from product to product. They depend on the length of the molecules and whether they are linear or form a branching network. Two common types of polyethylene are LDPE and HDPE.

LDPE is low-density polyethylene. It falls in the lower range of molecular mass and melting points. It’s often used in ‘soft’ and ‘light’ plastics such as plastic wraps, playground slides, food trays and computer hardware parts. HDPE is of course high-density polyethylene. It is used in plastic bottles, folding chairs, pipes and hard hats.

A big advantage of PE is that it is chemically very inert. It can safely be used to store or transport many common materials and chemicals for long amounts of time. A disadvantage is that it is not easily degradable in nature, although a few years ago a Canadian high school student discovered that there are bacteria who can eat PE (or have recently evolved to do so…)[3]. More importantly, PE is a thermoplastic polymer, which means that it melts when heated, so recycled PE can be cast into new shapes.

Polyethylene products are easy to recognize. Just find the little recycle logo that’s usually pressed on the bottom. If it says ‘PE’, ‘HDPE’ or ‘LDPE’ it is polyethylene.

Barium Sulfate
Melting point: 1580 °C, 2876 °F
Boiling point: Decomposes.
Molecular mass: 233.4u
Density: 4.5 kg/L

Why do chemists call helium, curium and barium the ‘medical elements’? Because if you can’t helium and you can’t curium, you barium. I’m so sorry, all good chemistry puns argon.

Barium sulfate occurs in nature as the mineral barite. It does not dissolve in water at all, which means it can easily be produced by mixing a barium-ion solution with a sulfate-ion solution, the barium sulfate will precipitate.

It looks like a white powder (although big crystals can be transparent, but that’s true for many salts). It is used in white paints under the name ‘blanc fixe’. It is also used as a paper brightener for photographic paper. It’s most important use is as a component of oil well drilling fluid, as BaSO4’s high density increases the density of the fluid.

Feasibility of the reaction
Feasibility: Low.

The things I said about nuclear reactions for ‘A Glass of Water’ apply to this reaction as well.


Particle Accelerator
Carbomega isn’t a thing and hydrogen isn’t new. I’ll just take a quick look at this puzzle’s namesake.

Particle accelerators are devices that speed up charged particles using electromagnetic fields. There are small ones such as cathode-ray tubes (CRTs) in old televisions. Those accelerate electrons, which cause the screen to emit visible light when they hit. A larger accelerator is the synchrotron, which is used to speed up electrons and then synchronizing them as a single particle beam in a ring, where they keep going in circles until the beam is used. These can be used for many analytical techniques such as X-ray diffraction and certain types of spectroscopy.

The best known accelerators are probably those that are build to collide particles in order to learn about particle physics. The large hadron collider (LHC) in Geneva is of this type. The LHC is basically a 27 kilometer long synchrotron. The LHC can speed up either lead nuclei or protons, which are hydrogen nuclei, making this puzzle (somewhat) accurate. The particles smash together with speeds very close to the speed of light, giving them an incredible energy per particle. I did a quick back-of-the-envelope calculation and found that if you gave such a ‘speed’ (the notion of speed gets a bit weird near the speed of light) to a one-gram object, its kinetic energy would equal the energy released by the Tsar Bomba, the biggest nuclear bomb ever tested... times three. Anyway, this causes them to fall apart and show their ‘inner workings’, the incredibly tiny subatomic things that make up each particle.