Question of the day

CatmanV2 said:

Curious indeed. Since gas and liquid are (I was taught) two different phases, on the face of it the question is non-sensical. I shall await the answer with interest

C

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WHS - Confused

Add another gas?

MrPea said:

How do you change a gas to a liquid without going through a phase change?
Why could this be useful?

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Im no chemist but isnt there something about the tripple state of water being a gas a liquid and a solid at the same time so i assume no phase change has taken place if its all three at once.

I presume that cooling is involved I.e. condensation, but why is this useful? Air conditioning?

Is this something to do with hydrocarbons? Isn't there a process where natural gas is partially oxidised which removes carbon monoxide, (the added benefit) and can then be transported in a liquid form?

I may have just made that lot up, but I seem to remember a company I looked at in my share dealing days did something like that.

There's a lot of thinking along the right lines. A couple of clues:
- The mostly commonly used chemical for this is carbon dioxide
- The temperature and pressure of the "triple point" of a chemical as far too cold and decompressed for this super-state.

I'll check in at lunch time to see if another clue is required. Navcorr, you may need to answer this later.

If memory serves, CO2 at STP sublimates. If you let it transition from a solid in a sealed (strong enough) vessel, you get liquid CO2

I assume therefore that if you apply pressure to gaseous CO2, you'd end up with a liquid but it still seems to me to be going through a phase change.

Best guess for use would be refrigeration.


C

CatmanV2 said:

If memory serves, CO2 at STP sublimates. If you let it transition from a solid in a sealed (strong enough) vessel, you get liquid CO2

I assume therefore that if you apply pressure to gaseous CO2, you'd end up with a liquid but it still seems to me to be going through a phase change.

Best guess for use would be refrigeration.


C

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WHS again, this was my thought process but there is still a phase change is there not?

Happy to answer but if others would prefer to wait for another clue??
Plus the rugby is starting soon.

Yes, the rugby is on indeed.
Next clue:
CO2 will start to act rather interestingly around its critical point... ~31 degrees and 1000 psi.

MrPea said:

Navcorr, you may need to answer this later.

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If I may step in as it"s unlikely to be "guessed". MrPea is referring to supercritical fluids (SCF) and their use.

An SCF is a chemical compound held above it's critical point by temperature and pressure. When a compound is SC it is neither a gas nor a liquid. It behaves as both. Can you argue that the change from liquid or gas to SCF is a change of state? Perhaps but strictly it isn't. Think of it as an alternate state rather than a change of state.

Typically, CO2 is used as it is cheap, inert and relatively safe. Water too. In recent years many "green" applications have been developed which will obviously be of interest to V6 & V8 petrol heads. Joking aside, for example, where volatile organic solvents can be replaced with an appropriate SCF. Dry cleaning being an everyday use.

As MrPea said previously there's been some good thinking. This isn't typical everyday chemistry though. However, SCF's are widely used in polymer chemistry which I just happened to study at Uni.

As such, given the unfair advantage, maybe someone else should nominate themselves the next QM. Perhaps CatmanV2 as SCF's are being used for refrigeration - just not in the manner stated.

Hopefully less specialised

What year was the two dollar bill last printed in the United States?

C

Never?

Navcorr said:

Never?

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Nope, sorry

C

Was it a special edition to mark the anniversary of something ?

spkennyuk said:

Was it a special edition to mark the anniversary of something ?

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Nope.

Again, I seem to have picked something needlessly obscure

C

There has been a number of series of the 2 dollar note. First one ended in 1966. In 1976 the series two was printed and this was only really issued for a year but in that time the series three came out. People believe that the note has been discontinued but is still available although finding one is pretty hard.

Sorry there's a two *billion* dollar bill? What on earth for?!

C

Sorry C was a miss type should say 2 dollar note not two billion.

CatmanV2 said:

Sorry there's a two *billion* dollar bill? What on earth for?!

C

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....the remake of Brewster's Millions - that's inflation for you!