Wikipedia:Reference desk/Archives/Science/2012 February 6

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February 6

Order of a mixture

Is there an article here in wk about why the order of elements of a mixture matters? (for example, hot oil + water, or acid + water or Nescafe + hot water). — Preceding unsigned comment added by 88.8.79.238 (talk) 00:17, 6 February 2012 (UTC)

For acid and water mixture, see Sulphuric_acid#Reaction_with_water_and_dehydrating_property99.245.35.136 (talk) 00:29, 6 February 2012 (UTC)

Yup. regarding the acids, our Sulfuric acid article explains why it matters:

"Preparation of the diluted acid can also be dangerous due to the heat released in the dilution process. The concentrated acid is always added to water and not the other way around, to take advantage of the relatively high heat capacity of water. Addition of water to concentrated sulfuric acid leads to the dispersal of a sulfuric acid aerosol or worse, an explosion. Preparation of solutions greater than 6 M (35%) in concentration is most dangerous, as the heat produced may be sufficient to boil the diluted acid: efficient mechanical stirring and external cooling (such as an ice bath) are essential.

As for mixing hot oil and water, if the oil is above 100 C, adding water is going to result in vaporisation, and ejection of hot oil. This is why it is extremely dangerous to try to put out a cooking-oil fire with water - you can end up with a fireball - see Chip_pan_fire#Fire_hazard. AndyTheGrump (talk) 00:34, 6 February 2012 (UTC)

I've also noticed that you want to add cocoa powder to hot water, not the reverse, or it will stick to the bottom of the cup. StuRat (talk)

For Nescafe + hot water, you've apparently never seen what happens when you add powdered substances to superheated microwaved water. The temperature of the water can exceed 100 degrees, and adding the powder can trigger a mess, and even dangerous, explosion. Same goes with hot cocoa powder. Dominus Vobisdu (talk) 01:36, 6 February 2012 (UTC)

I just use hot tap water, no nuking here. StuRat (talk) 01:50, 6 February 2012 (UTC)

Frankly I imagine that the issue is less about explosive water (which is pretty uncommon) but the fact that if you add the powder last it becomes very hard to mix in. I've done in backwards many times and what you end up with is a lot of powder floating on top, vigorously resisting making a mixed liquid. If you do it the other way, that doesn't happen. --Mr.98 (talk) 03:18, 6 February 2012 (UTC)

Yes, because it's all stuck to the bottom. :-) I think adding a bit of hot water, then the cocoa powder, then the rest of the hot water, is the best approach. StuRat (talk) 05:05, 6 February 2012 (UTC)

I concur with StuRat, but additionally stir the initial water + powder mix vigorously with the teaspoon (why do we never say cocoaspoon?) before topping up. This enables you to reverse the first two steps and add some water to the dry powder, which is sometimes more convenient, as you can have the cocoa jar put away again before starting to mess with the kettle, thus decluttering the work surface. It's all in the therbligs! {The poster formerly known as 87.81.230.195} 90.197.66.42 (talk) 12:46, 6 February 2012 (UTC)

For what it's worth, I treat hot chocolate powder like cornflour: dry stuff goes in mug first, then add splash of water and stir thoroughly to make a thick paste. Then water down the paste, stirring constantly. No clumps at the bottom! Brammers (talk/c) 16:42, 6 February 2012 (UTC)

For Americans who might be confused — Brammers is talking about cornstarch, which for some odd reason Brits call cornflour. --Trovatore (talk) 16:53, 6 February 2012 (UTC)

The mnemonic I was taught: You're doin' watcha otter when you add the acid to the water. --Trovatore (talk) 16:45, 6 February 2012 (UTC)

The mnemonic I remember is "don't do what I did that time many years ago when I added water to acid and the flask shattered". DMacks (talk) 17:33, 6 February 2012 (UTC)

Well, good for you if you can remember for sure which one you did. In junior high school I had a similar experience (sodium thiosulfite solution plus acid --> cloud of yellow gas that sent everyone out of the room) but I thought I had done it right. Maybe I did add the acid to the water but just too much at once, or something. At this remove it's impossible to be sure. --Trovatore (talk) 19:05, 6 February 2012 (UTC)

"May her rest be long and placid,

she added water to the acid.

Quite forgot what we had taught her,

add the acid to the water"

- I guess this worked as a mnemonic, as I last saw it thirty years ago, and reading this thread brought it all back. (this is my first wiki edit, so please feel free to correct any mistakes I have made with format) TrohannyEoin (talk) 10:31, 8 February 2012 (UTC)

Boiling points and tripple points for monatomic gasses

Does anybody know where I can find the (notional) boiling points (at standard pressure) and the triple point for monatomic gasses including H, O, N ? I assume these must be calculated/estimated values as they will not be stable at such low temperatures. Thanks Keit124.182.1.238 (talk) 02:50, 6 February 2012 (UTC)

See our articles on hydrogen, oxygen, and nitrogen, under "physical properties".--Shantavira|^{feed me} 09:01, 6 February 2012 (UTC)

I wish it was that easy, Shantivira. These Wikipedia articles, although describing the elements H, O, & N, actually give the properties for the molecular form, H2, O2, and N2. If you look up the NIST online database for H2, O2, and N2, you get the same values as given in the WP articles. Keit121.221.76.67 (talk) 12:28, 6 February 2012 (UTC)

Then the only gases you're talking about are the noble gases Helium neon Argon Krypton Xenon and Radon. Dmcq (talk) 14:03, 6 February 2012 (UTC)

No, definately not talking about the noble gases. Monatomic gasses such as H, O, and N are not stable at low temperatures (and pressures), but they CAN and DO never the less exist - that's why I need values for them. I could find all manner of properties for them, but not boiling and triple points. Keit124.178.157.111 (talk) 15:20, 6 February 2012 (UTC)

Don't you see a problem with high temperature low pressure solid gas? Dmcq (talk) 16:10, 6 February 2012 (UTC)

You are essentially asking a counter-factual. Monoatomic H, O, N can never form liquids or solids because long before they reach that state they will first form diatomic molecules. Hence it makes no sense to ask what their boiling points / triple point would be since they will never reach such a state without forming molecules. I don't see how such notional values could be useful. More to the point, I don't think there is anyway to usefully calculate such values. The interatomic forces between these monoatomic gases lead to pair-bonding, but you want to calculate how the interatomic forces lead to the formation of liquids and solids while somehow preventing pair-bonding. Whatever answer you get from such a calculation would depend strongly on the modifications you made in order to prevent the formation of pair bonds, and at that point it wouldn't be representative of any true behavior for the monoatomic gas. Dragons flight (talk) 18:36, 6 February 2012 (UTC)

It seems valid to ask what the properties are, though maybe there are no published values. Once created, unstable forms can exist, it's just for a limited time - in some cases, years, in some cases, minutes, in some cases picoseconds. But they can exist. Monatomic gasses are extremely unstable at standard temperature (~298K) and pressure (~1 Bar), you can certainly find thermodynamic data (eg specific heat, enthalpy, etc) for them (eg Rose & Cooper, NIST, etc etc) - presumably these are calculated values. And the common forms H2, O2, N2 are quite unstable at 6000K, but you can find calculated properties for them at 6000K. Don't forget that gases unstable below certain temperatures can be made so by increasing pressure. Judging by the marked upward tilt of specific heat at low temperatures and 1 bar, the triple point and boiling point of monatomic oxygen must be close to standard temperature and pressure, that of H must be very low. Ratbone121.221.96.117 (talk) 01:22, 7 February 2012 (UTC)

Where on NIST did you find thermodynamic data for monatomic gases? The boiling and triple points are statistical properties resulting from the interaction of the molecules. I don't see how you can expect to determine a statistical property caused by interaction if you neglect the most significant aspect of that interaction, the pair bonding. --140.180.7.220 (talk) 06:57, 7 February 2012 (UTC)

Go to the NIST website http://webbook.nist.gov/chemistry/form-ser.html, key in, say "H" in the chemical formula filed, click the Search button, and up will come a page headed "Hydrogen atom" and showing an index of what they have. Choose "Gas Phase Thermochemistry Data" from this index - you'll then get a page with a table of key thermodynamic data, and the Shomate coefficients so you can calculate specfic heat etc at any temperature your heat desires, at standard pressure, including low temperatures where H is most unstable. If you prefer, you could also go to your local university's library and look up the NIST-JANAF tables. Or look at Rose & Cooper and similar standard texts. The 4th ed of NIST-JANAF has data at standard pressure for all monatomic gases down to 100K where H is extremely unstable. But none have the triple point, unfortunately. You are quite wrong in your comment about calculating boiling and triple points - you have missed a key part of my original question - but it is somewhat complex to explain - I will see if I can give a simplified explanation in a separate post. Keit121.221.73.82 (talk) 13:55, 7 February 2012 (UTC)

If the reaction you are interested in takes orders of magnitude longer than the substances involved are stable for, then for all intents and purposes the reaction can't happen. That's why, for instance, you won't find any data about hadrons containing top quarks. At first glance, it makes sense to talk about top quark hadrons, but they would take longer to form than the top quark is stable for. That means they don't actually exist and there is no meaningful data, even theoretical, for them. The same is true for liquid monoatomic hydrogen, oxygen and nitrogen. --Tango (talk) 12:44, 7 February 2012 (UTC)

"If the reaction ... takes...". I'm certainly aware of that, though I know nowt about quarks. The reactions I am interested in may or may not be noticeably affected by the presence of low concentrations of monatomic H, O, N, and perhaps C. I'm NOT interested in their liquid forms. I'm only interested in their gas forms, i.e., their behavior above the line joining the boiling/sublimation point to their triple point (which is a straight line if plotted on a reciprocal progression temperature scale). To do that I need to know (at least approximately) where these points are. Keit121.221.73.82 (talk) 14:43, 7 February 2012 (UTC)

I meant "reaction" very generally - I was referring to the condensation/evaporation. I don't understand how you can not be interested in their liquid forms. You asked about their boiling points. Boiling is something liquids do. It doesn't make sense to talk about the boiling point of anything that isn't a liquid. --Tango (talk) 22:26, 7 February 2012 (UTC)

I've just realised that I have been writing "boiling point" where I should have written "critical point". I don't know why I did that - must be not enough sleep or too many parties. My question may make more sense now. My appologies. But those who understand gas phase reactions could probably have seen thru it anyway. Tango is probably still confused, as he now thinks it only makes sense if I am interested in the state at temperatures below the critical temperature, and pressures above the vapour pressure, which is a liquid. No I'm not interested in the liquid state. To see why, consider a broad analogy: the notional absolute zero temperature of metals. To calculate the electrical resistance of conductors, which is approx proportional to temperature, electrical engineers use a simple formula incorporating absolute zero

R2 = R1 (T2 + T0)/(T1 + T0) .   T2 is the temperature of the conductor;  T1 is the temperature (usually 20C) at which R1 is the 
resistance listed in tables.

This formula assumes that the resistance is a straight line relationship and all metals have zero resistance at notional absolute zero (T0). They commonly use a value of -235C, whereas the thermodynamic absolute zero is -273.15C. They use -235 because it compensates for a number of factors that make the relationship depart from an exact straight line. It DOES NOT mean that electrical engineers are interested in what metals do at -235 or -273C, which mostly is not what this usefull practical formula predicts. They want to know the resistance at operating temperature, usually between 0 and 75C. In a broadly similar manner, I am not interested in liquids. But to work out the behavior of monatomic gasses at "low temperatures" (up to around 900K for oxygen) I would like to know what the NOTIONAL state transition temperatures are. Keit124.182.169.5 (talk) 01:38, 8 February 2012 (UTC)

You shouldn't think of T0 in that equation as being absolute zero. That equation is a first order approximation and T0 is the constant you happen to get when you plot a straight line of best fit to the relevant data points. It's not entirely coincidental that it comes out as being fairly close to absolute zero, but that isn't a useful comparison. If you are working with first order approximations, you need to determine your constants based on data points near the point you are interested in. If you try and base them on points a long way from those that you are interested in, especially points that are physically meaningless, you will get massive errors. --Tango (talk) 12:31, 8 February 2012 (UTC)

Tango, I think this is a case where you and I agree in principle, we just use different language. I know T0 is not TRUE absolute zero - I said so above. But to electrical engineers it IS a "notional" absolute zero - the notional/fictitous temperature where the resistance of any metal conductor is notionally zero, and there's nothing wrong in thinking that way - so long as you are aware that the thermodynamic absolute zero is different. We ARE all aware of the thermodynamic absolute zero. As far as errors are concerned, you are right in principle, however the accuracy with this simple formula, in common use, is most certainly good enough over the temperature range that electrical engineers are interested in. It is certainly NOT necessary to choose data points close to the desired point - the standard -235C for T0 and 20C for T1 work just fine.

Now, I guess any WP fans out there, who might have an answer to my original question about notional triple and critical points, have gone elsewhere due to a) my use of "boiling point" where I meant "critical point", and b) the tangents introduced by chaps who want to say I haven't asked a valid question, without carefully reading and understanding the question, so perhaps we should leave it at that. It's been fun though, and hopefully has caused a few readers to think about things they don't normally think about. Keit121.221.165.218 (talk) 12:56, 8 February 2012 (UTC)

There is something very wrong with thinking in that way - it's not true. The resistance of metals at -235C is not zero. That equation is only a good approximation in a fairly narrow range, as is generally the case with first order approximations. You misunderstand what I mean by "data point". -235C is not a data point, it's a constant derived from data points. The number -235C was determined by considering the actual resistances of various metals at various temperatures and drawing a line of best fit through them. Those actual resistances will have all been measured at temperatures near the temperatures of interest to users of the equation - they won't have measured resistances near -235C. Once you've got your line of best fit, you work out the equation of it and you find that there is a constant of -235C. That constant doesn't have any physical significance and would be completely different if you were going to come up with the similar equation for use in a different temperature range. --Tango (talk) 19:42, 8 February 2012 (UTC)

Tango, everything you've said in your last post is true,and in complete agreement with what I said, except for your first and last sentences. (a) there is nothing wrong with thinking that way - almost everything in science & engineering is just a mathematical model, and not completely proven it's only necessary that such models give good results. (b) it hapens that the -235 value gives adequately accurate results over the temperature range engineers are normally interested in (typically 0 to 75C), but you'll find that if you try a quite different range, say 100 to 300 C, the notional absolute zero is not very different (about -233C in this case, as I recall). The true relationship is very close to a straight line. Yes, the formula I gave does not have any physical significance whatsoever - doesn't matter, it works. Same with thermodynamic properties of elements and chemicals - Engineers and others typically use the so-called "NASA" method, or the Shomate formula, or even the "3-lines" method. NASA and Shomate formulas look completely different, have no physical basis at all, but they curve fit over about a 4:1 temperature range to 4 place accuracy, up to 5000K (NASA) and 6000K (shomate). The three-lines method is slightly less accurate, but usually good to 3 places from 200K to 6000K. And absolute no physical basis or logical derivation. It just works. Enough said. Keit121.215.22.13 (talk) 22:31, 8 February 2012 (UTC)

I never said first order approximations don't work - they are incredibly useful. That doesn't make -235C absolute zero in any meaningful way, though. It is just a constant that you get when you fit a straight line to some data points. It doesn't have any physical significance - nothing interesting happens at that temperature. You can't use the fact that such constants are useful as an argument for the idea of a critical point of monoatomic hydrogen making sense. It can't exist as a liquid, so it doesn't have a critical point. --Tango (talk) 01:08, 9 February 2012 (UTC)

At low pressures (typically <0.1 Bar) (or at a notional zero pressure - sorry Tango, I couldn't resist that one) gasses display three regions of specific heat: 1) a flat, temperature independent region at low temperatures where the specific heat comforms to the classical formula based on kinetic degrees of freedom. 2) A region at high temperatures where specific heat is higher than the classical kinetic degree of freedom, and slowly increases with temperature due to bond excitation and electronic effects, and (3) a transition at medium temperatures (typicallly around 800 to 2000K, depending on the gas) where specific heat relatively rapidly changes from (1) to (2). At higher pressures, Region 2 is for all intents and purposes unchanged. Region 3 hardly changes - for engineering purposes Region 3 can be regarded as pressure independent. But Region 1 IS pressure dependent. Increasingly with increasing pressure, specific heat INCREASES with DECREASING temperature. Why? Because at 1 Bar, it must intercept the triple-point / critical point line at the boiling point (which by convention is defined at 1 Bar), and this is at generally greater than the gas classical value. More signifantly, at critical pressure, the specific heat of a gas must INCREASE with falling temperature to intercept exactly the critical point, where the specific heat is INFINITE. In other words, gasses have, at real pressures, a temperature where the specific heat is a minimum - this temperature is in the range 500 to 2000 K depending on the gas. Below this temperature you get a range of negative slopes depending on the pressure-temperature location of the triple and critical points. Or, looking at it another way, if you know the low pressure curve of specific heat vs temperature, and you know the triple and critical points, you can with the right mapping, predict the specific heat vs temperature curve at any desired pressure.

THIS TRIPLE & CRITICAL POINT DEFINING LOW TEMPERATURE BEHAVIOUR IS SEEN WITH MONATOMIC GASSES. For H the increase is negigible at 1 bar (might not be at higher pressures - I haven't seen any data), but for O the increase is very marked at 1 bar, the curce being very steep at 200K - the lowest temperature at which I have trustworthy data. Carbon gas (both C1 & C2) shows a distinct negative slope at 1 Bar in Region 1 too. Please explain that if you think such gases don't have notional critical points.

I think this has gone on long enough under this Question Heading. We must have set a record for the longest discussion in the Science Desk. May I suggest that if Tango, or anyone else, wants to continue down this side path, then create a new question, headed "Thermodynamic behaviour of monatomic gasses" or some such, and ask "Can notional critical, boiling, and triple points be defined for monatomic gasses?" or whatever you think. I may then respond to that and we can allow the Wiki system to archive this question. Keit120.145.8.148 (talk) 15:36, 9 February 2012 (UTC)

Relife from pain

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the talk page discussion (if a link has been provided). --Jayron32 04:48, 6 February 2012 (UTC)

The Ostrich & Disemboweling

The wikipedia article on the Ostrich mentions that they are capable of disemboweling people. Several other websites repeat this fact but without any citations. Are there any confirmed stories of ostrich disembowelment? --188.220.46.47 (talk) 14:56, 6 February 2012 (UTC)

They're certainly capable of causing eye injuries to people, but I can't find any evidence of ostrich disembowelment in recent history. That doesn't mean it's not completely possible - cassowaries are apparently especially aggressive and do have sharp rear claws on their feet perfectly capable of disemboweling or other painful injuries. A cassowary did kill a boy in 1926 but no bowels were involved. §everal⇒|Times 17:23, 6 February 2012 (UTC)

What about other predator disemboweling? --CGPGrey (talk) 17:34, 6 February 2012 (UTC)

Does a locomotive count as a predator? Ostriches will attack all kinds of things but it's not clear that disembowelment is a frequent result. §everal⇒|Times 18:01, 6 February 2012 (UTC)

Human disembowelment is a quite specific procedure of which very many animals are no doubt capable should they be so minded, but to categorise specific animals in this way seems not to be particularly useful or encyclopedic. It's not as though they routinely go around disembowelling people.--Shantavira|^{feed me} 19:06, 6 February 2012 (UTC)

I disagree that it is a "specific procedure." We are not talking about a precise and specific procedure. There are many ways that the abdomen could be cut open and some or all internal organs torn out. Edison (talk) 16:18, 7 February 2012 (UTC)

MAGNETIC GENERATORS - Worth using?

I REALLY don't care all that much about long-winded, techincally-termed details of how these things work, or are claimed to work. I'd just like to know in LAYMAN's TERMS: A. Do they work at all?; and B. Are they capable of substantially reducing electric bills or operating any electrical appliance (110 or 220V) independently with little "Supplied Electricity" [wired power companies] use? Much thanks. I don't trust them to refund ALL my money for their books. — Preceding unsigned comment added by Scizottstheb (talk • contribs) 16:53, 6 February 2012 (UTC)

Well the first link I read, from "thefreeenergygenerator.org" talks about "perpetual motion" and doesn't explain the source of the energy, except they seem to confuse force with energy, so I suspect that the whole thing is a scam, unless, of course, they are selling a device to stop your meter from recording the real energy used, then they are illegal. The same site advertises running your car on water! Draw your own conclusions. (or read this) Dbfirs 17:24, 6 February 2012 (UTC)

In layman's terms: no and no. §everal⇒|Times 17:28, 6 February 2012 (UTC)

This saying comes to mind. Roger (talk) 09:01, 7 February 2012 (UTC)

Do not give these criminals your money. They are liars and thieves. There is no such thing as a free lunch. People have been scamming money out of people for literally centuries with crud like this. Steorn is another modern example. Liars and thieves. — Preceding unsigned comment added by 217.158.236.14 (talk) 14:47, 8 February 2012 (UTC)

Should I turn off the LCD before switching off the surge protector?

Thanks. — Preceding unsigned comment added by 66.108.223.179 (talk) 17:19, 6 February 2012 (UTC)

I assume you mean an LCD computer monitor. If it's Energy Star compliant, the monitor will go into standby mode if not used for a few minutes, so there's no need to turn it off in either place. If the surge protector also powers other things you need to turn off, then it's OK to turn it off there first. I also do this with my non-Energy Star LCD monitor (stupid thing shuts off the screen except leaves the back-light on). Also, if the computer is on the same surge protector, then you do need to turn the computer off using the menu first. StuRat (talk) 19:35, 6 February 2012 (UTC)

Diesel hybrid car

Why don't they make hybrid diesel cars? Is it a technical thing? — Preceding unsigned comment added by 166.205.136.209 (talk) 20:08, 6 February 2012 (UTC)

Diesel-electric transmission#Production-ready cars -- Finlay McWalterჷTalk 20:15, 6 February 2012 (UTC)

Electric transmission (using electric means to convert engine RPM and torque to road-appropriate speed and torque) should not be confused with Hybrid electric drive (using an electric motor for propulsion to assist an internal combustion engine). Electric transmision dates back at least to the 1920's but has never been popular as the conventional hydro-mechanical automatic transmission does the job just as well and is a lot lighter. Recent developments in better magnetic materials is changing this picture. Re hybrid diesel-electric propulsion, it will happen but there is less incentive than hybrid gasoline-electric because diesel engines are more expensive than gasoline engines, and the main advantage - fuel efficiency - is significantly discounted by the much greater efficiency of diesel engines at larger sizes. A diesel engine, more efficient that a gasoline engine at full throttle, is still more efficient at part thottle than is a gasoline engine. But in a hybrid vehicle, if you don't need high power at certain times during driving, the gasoline engine can be simply shut down. Keit121.221.96.117 (talk) 04:30, 7 February 2012 (UTC)

Any US cars with this feature?

I press a button on the dashboard. Later, I press it again, or another button, and the car tells me how many gallons of gas have been used between the two button presses. No, I don't care about the feature of seeing instantaneous calculated mileage, because slope snapshots are useless (to me) when I'm not constantly staying at the same mileage. 20.137.18.53 (talk) 20:45, 6 February 2012 (UTC)

Some cars have trip computers, which have a button to start the "trip" and another to end it. However, the ones I've seen report total miles traveled and average MPG over the trip, from which you could calculate gallons of gasoline used, but don't actually report the gallons. StuRat (talk) 20:50, 6 February 2012 (UTC)

A "gas used" readout was on some of the last years of Pontiacs. The dashboard display could select "gallons of gas" and it would keep adding up fuel as it was used. It could be reset to zero anytime, such as when the tank was filled, or when a trip began. The display could alternately show "miles remaining" "miles per gallon, or "% remaining before oil change needed." Edison (talk) 00:45, 7 February 2012 (UTC)

Also bear in mind that a car fuel gauge is not a precision instrument.--Shantavira|^{feed me} 10:14, 7 February 2012 (UTC)

Yes, that's why I ask. :) 20.137.18.53 (talk) 15:35, 7 February 2012 (UTC)

The General Motors gas used readout worked off the fuel pump, and consistently read about 5% less than what the gas station pump said the car had used, when it was filled each time. The needle on the fuel gauge was far less accurate, dropping slowly as the first few gallons were used, then dropping rapidly at the end. It has a sensor in the gas tank consisting of a float on a swivelling arm, which connects to a potentiometer. I've no idea if the inaccuracy came from a failure to allow for varying relationship between fuel level and arm angle, or the varying relationship between the change in fuel level and the varying cross-section of the fuel tank.With computers in the car's electronics, it would have been trivial to use a lookup correction table to make the dial (or digital display) accurately reflect the fuel remaining. Edison (talk) 16:15, 7 February 2012 (UTC)

It's because between full and almost full the arm doesn't move at all. Between almost empty and empty, the same happens. (If you'll take Cracked for source, its here.) Grandiose (me, talk, contribs) 13:52, 8 February 2012 (UTC)

What would be good for what I'm talking about would be a flowmeter on the line that carries the fuel from the fuel pump to the engine, because I want to know how much volume of gas has been consumed between time A and time B. This would not be frustrated by tank fill-ups between button presses. 20.137.18.53 (talk) 17:33, 7 February 2012 (UTC)

Saccharides

What is the most stable form of glucose in the crystaline, solid phase - open chain, furanose, pyranose or some other form? How does the chain length affect the stability of said form compared to the others? Plasmic Physics (talk) 21:52, 6 February 2012 (UTC)

If you read Glucose you can answer much of your homework question yourself. If you can't find your answer, please look closely in the section titled "cyclic forms", especially the last paragraph. But the entire "Structure and nomenclature" section is good reading as well in this regard. You can also follow bluelinks from that article, especially to articles like furanose and pyranose, to find the other answers to your homework problems. --Jayron32 01:45, 7 February 2012 (UTC)

OK, so aldohexoses exist as the pyranose form in the crystaline solid phase. What about pentoses, heptoses, etc. What about ketoses?

P.S. It is not a homework question. Plasmic Physics (talk) 04:22, 7 February 2012 (UTC)