Posts Tagged ‘water’

The Edge: This time its HARDCORE!

November 1, 2011

   Before next year (2012) is out, I plan to have taken you to the edge of the unknown, and give you vision beyond mere sight.  To guide you up the more accessible foothills of the unknown on a voyage of discovery leading to an intellectual vantage point from which you will understand why, given nothing but natural processes, emergent self replicating life seems inevitable, rather than improbable.

-Damn straight! If you are going to do open n accessible science, make it interesting! Shining the magic light of knowledge on the hidden origin of life seems to be a pretty entertaining place to start 🙂

The first footstep on the journey of discovery

   Further, now that many know my real name, I can openly link up with other high profile groups promoting science education (to be announced) to publish this work in the peer review literature.  And sure, why not, let’s be bold and set a goal of getting this work published in one of the top research journals like Science or Nature.

   How does this work start? Why with a good drink of bacardi of course!

And I can fully assure you that by this time next year, you will see SOO much more than an amber, highly volatile liquid that is well know for its intoxicating properties on many carbon based life forms!

DON'T PANIC, IT'S ONLY SCIENCE!

   ….and yeah, if anyone’s got a wizard name for this epic endeavor, I’d love to hear it it the comments section below 🙂

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Sunday 31st (Sodium Boom n beyond)

August 4, 2011

Spent the morning very happily going over the potassium footage.  The whole thing is a symphony of physics and chemistry that eventually I decided it would take too long to explain, so I just put up the explosion footage.

It had been raining in Ridgecrest and this clearly was  a freak event.  The standard greeting in Rigercrest between the notably fat folks seems to be ‘hot enough for you’, and not without reason, I think it’s been over 100C every day I’ve been here.  However for the afternoon I decided I would give blowing up the sodium a go.  Now I have lots of sodium, and the scale and geometry is different.  Eventually I decided the way to do it was to get a stick over a reasonable sized vat, which meant that I could lift up the sodium from a distance, have it swing over the vat, then be lowered in.  Sodium is significantly less dense than water, and so would need to be weighted.  The sticks were typically about 10g, so eventually I wrapped up about 4 sticks in aluminium foil, attached weights to them and lowered them in to the vat from a distance.

Initially the reaction seemed really quite slow, to the point where I was wondering how this was going to pan out.  Indeed it took over 10 seconds before the first ‘explosion’ (compared to about 1second for the potassium experiment).  I, for my part am mostly certain this is related to the metal boiling.  However, when it really blew up (and did so quite convincingly) it really made a mess of the container.  Again, the hydrogen burning wasn’t really even a relevant factor, it’s just the adiabatic expansion of the gas released by the reaction.  In this case 40g gives about 40L of gas.  Thats a lot of gas to release in a 5L container!  On inspecting the aftermath it became clear that large chunks of sodium had been thrown clear of the reaction, not just unreacted, but unmelted!  This for me was a stunning observation!  It shows that whatever the reaction that takes place, the rate that heat is generated at the surface is MUCH higher than the rate the heat can be conducted away from the surface.  Sodium is an absolute bitch for making a mess!  Small amounts of sodium had been sprayed all over the tripod, and stripped the paint.  They had then picked up water to make conc. NaOH, draincleaner which will first turn you skin into soap, before chemically burning you.  The stuff was everywhere!  Cleaned up as best I could (again I was on the inaccessible dirt road to nowhere in my little ravine).  Headed back to LA.  Stopped off to see Lisa n Howard n pick up a shower, which I more than needed.  Initially i wanted to get up onto mnt Wilson early, for sunset, but got chatting to Lisa and that never happened.  It was full dark before I set out on the nightmare trek across LA by dark.  It didnt help that I managed to set the GPS wrong, and ended up on the long drive through the horrific twistiy winding roads of the Wilson range (rt 2).  There had been rain here too, and while the road was all but deserted, top speed was about 40 mph and ‘tire killing rocks’ materialized out of the gloom on a regular basis.  Driving that 20 miles was an incredibly intense experience, ultimately driven by ‘do u want it or not’.  I did, I wanted to get up on mnt wilson and do something on light pollution and LA.  I got there about midnight, and got my piccies!

Sat 30th July (Big Badda Boom!)

August 1, 2011

It’s crazy, I keep on meaning to get the planes going, it just never quite happens.  Thinking back it probably is a contributing factor that I never get more than 3 hrs continuous sleep (changing battery packs).  Hmm maybe I should have invested in one of those large battery packs, or just jury rigged one myself.  So on the evening on the Saturday I decided it was time to get rid of the potassium.  The stuff is a damn liability in a hot car.  Sure it’s under oil, in an airtight bottle, in an airtight metal can, but even so, its just a liability to have in a car that is your ‘home’.  Turns out I had about 12 grams.  Initially I used my ‘dunking’ apparatus for 4 grams, to show that it would shatter glass easily.  So inside the dunking kit I had a glass.  This is of course the smart way to do it if you don’t want broken glass everywhere.  The kit was a bit war torn by travel and needed some patching together.  I also had to find a ‘safe’ place to do this.  Safe in this case means sufficiently isolated that you are not going to disturb anyone (easy enough in the high sierra) and far enough from vegetation as to not cause any fires.  Eventually found a ravine that would do the job, but damn was it exciting getting my little NYer down those dirt trails for all terrain vehicles.

Turns out the apparatus stuck a little, but the end result was still more than acceptable!

You will notice in this reaction the immerser is fired out.  Turns out on the immerser there was still unmelted and unreacted potassium.  This for me was a fascinating discovery in that it shows the rate that the heat is generated on the surface greatly exceeds the metals capacity to conduct heat!!

Also led to one of those ‘thats why we wear facemaks’ type moments:

I then basically emptied the rest of the potassium out (about 7-8g in total) and wrapped in in aluminium foil and attached it to the emmerser.  Knowing how these things can scale in trecherous fashions, I moved the cameras and myself further away this time.

The 8 gram reaction was again very satisfactory, and I was glad to get rid of that potassium.

The wind regrettably was very high, and only later did I get a ‘sock’ on the mike, meaning most the audio I got here was mostly wind noise 😦  .  On the grand scale of things that was a small loss.  With these sorts of en-devours you can be so frequently screwed by the smallest absent minded moment (take for instance the previous day, when just not setting the focus on the camera resulted in a nights wasted effort).

By the time it was all over I was exhausted, the more so after I had nursed the car out form the dirt trails to nowhere.  So I rolled the car back to where it was kinda overlooking Ridgecrest and watched the over the Sierra Nevada Mountains.  It was beautiful with the brillant yellow sun peering through the clouds, torn by the wind, shining through into the valley in the foreground filling it with a warm glowing orange to the misty mountains beyond.  It was while I sat there in the silence of the high plains musing on how well the potassium thing had gone, that I suddenly realized that I hadn’t really talked to anyone for days, well, least ways anyone who actually knew my name.  Did think about heading down into Ridgecrest, simply to talk to someone on skype, or phone (mine doesn’t work out here), but I was exhausted, and the sunset was pretty, and by the time it had sunk below the mountains, fatigue had caught up with me.

Potassium explodes without Hydrogens help

June 20, 2011

Thus far almost all the stuff I’ve done on the alkali metals has been on ~250 mg quantities.

Self preservation says, “Start Small!”, and with good reason, the reactions of alkali metals with water are known to scale in treacherous fashions.

In the first instance I went for 1.6 g of potassium and 3.5g of sodium.

Note here there is not the slightest hint of green gas with the potassium!

Now the potassiums the one I’m going to focus on for the moment, simply as when this is played back at about 1/100ths speed it becomes clear that the hydrogen burning plays essentially no part in the violence of this reaction.

Fascinatingly the explosion appears to go in two stages here!

So potassium, molecular weight ~40, so 1.6 g is 0.04moles. 2moles of potassium gives a mole of H2 , so this reaction will produce about half a liter of hydrogen.  Just for scale the jug is about 3 liters.  It’s also fascinating to see the ‘springiness’ around this generated gas.

Why is Potassium gas Green?

June 18, 2011

So my interest was really spiked here when I found that when reacting with water, potassium gives off a green gas!

While the green of potassium gas has been known about for over a century, being found in Encyclopedia Britianica articles as far back as 1911, the origin of that green color is proving a little more elusive.

If you know what you are doing it’s relatively easy to observe.  250 mg of potassium is ‘the right’ scale to work with.  Much smaller and it’s all over before you get a chance to do anything, much bigger and you run into problems with the metal exploding, or the hazards of hydrogen build-up.  All you need is a heavy glass vessel of about the dimensions of a wine glass.  Insert a burning acetone taper through a small hole in the top of the vessel and to burn out all the oxygen, and then drop in your potassium.  The green color is easily visible.

I’m tempted to propose it’s due to the solvated electron, which is a hot research topic at the moment as it’s part of the principal mechanism by which radiation damage happens to DNA.  It’s known to be stable and blue in liquid ammonia, but survives only picosecond in water.

A bead of Sodium Potassium alloy in anhydrous liquid ammonia. The blue colouration is due to the presence of solvated electrons

It’s an interesting suggestion, but I think the observation that you get the green color when there is no water around pretty much kills this idea.

So how do you get a green gas.  Well the only other metallic gaseous vapor I’ve seen was mercury which I once boiled to test the calibration on a thermocouple.  That has no color at all that I can remember.

Well as you will recall virtually all the gases are colorless, e.g. all the Noble gases (helium, argon etc) and all the first period gases (nitrogen, oxygen, and mostly fluorine).  However the heavier halogens have colored vapors that get more heavily colored as you go down the group.  Chlorine, light green, bromine, brown etc.

Chlorine (left) and bromine (right).

The reason these gases have these colors is the same reason the sky is blue, Rayleigh scattering.  That’s related to the polarizability of the molecule.  This is a very different mechanism from the electronic transitions that give the classical flame colors of the alkali metals!

It’s well known that all the alkali metals have stable bound states as diatomic molecules, similar in electronic configuration to hydrogen.  IF K2 had a similar polarizability to Cl2, it may well be green like chlorine!  Regrettably finding the polarizability K2 is not as easy as it sounds.  A significant difference between H2 and K2 is the bond energy.  H2 has a bond energy of about 400kJ/mol, while K2 has a bond energy of ~50kJ/mol.  For reference, the hydrogen bond, the thing that holds water together as a liquid, has a bond energy of ~20kJ/mol.  If you heat any bound state and eventually the species will gain enough energy to separate and become individual species.  With water this happens at about 100 oC (boiling, ~400 K).  For hydrogen it’s about 3000 K.  You can actually do the real calculations, it’s just I’m too lazy at the moment, and so I’m just going to do a linear extrapolation between these two.  That gives K2 breaking up at about 2-300 oC.

Well that would fit nicely with green gas being evolved at lower temperature, but as the temperature rises, the diatomic species break up, and the relevant polarizability of the molecule, and hence the Rayleigh scattering, and hence the color is lost.

Great, so if this is a working hypothesis, then the diatomic metals should match their corresponding halogen right?  The bummer is sodium.  Sodium gives off a blue vapor when it boils.  Fluorine is almost colorless.  ARSE!

The game is not over yet!

I’ve decided I need to see sodium vapor for myself, but how to do it with only the junk I have to hand!  What I really need is a nice small sealed silica tube that can take temperatures over a thousand degrees C.  Hmmmm, thinking, thinking…..