Brainiac's alkali metals were FAKED!

Creative commons material at:
http://www.youtube.com/user/thunderf00tCC

On the road I will be putting a journal up of my tour of the US on:
http://www.thunderf00t.org

So why does 7 grams of lithium release more energy than 130 g of cesium reacting with water.

Well 7 g of Li and 130 g of Cs contain about the same number of nuclei. Now you could just do the experiment of dunking both of these into water, and seeing which generates the most heat. Its a little impractical due to the cost of cesium. The violence of the reaction probably wouldnt be that big of a problem. Cesium melts at almost room temperature, so you just put it in a syringe and inject it into water.

However one of the nice things about chemistry is that it allows us to calculate things. In this case we can calculate the relative energy of Cs and Li dissolving in water.

Li(m) + H2O = Li+(aq) +.5H2 +OH-(aq)

Cs(m) + H2O = Cs+(aq) +.5H2 +OH-(aq)

Well as we are doing a comparison, there are components that are energetically equivolent in both these equations so we can cancel them.

Li(m) = Li+(aq)

To calculate this we need to know three values, the energy to atomize the metal, the energy to strip an electron off it, and the energy to dunk that atomized ion into water at infinite dilution. Thankfully chemists are nerdy types and all these values are known.

Put the numbers in and you find that Li(m) and Cs(m) reacting with water are virtually energetically identical. However in the case of equal masses of Li and Cs, the lithium will release about 20x as much energy (as you have 20x as many atoms).

So why does one explode and not the other. I think several factors are relevant.
1) the area of water: metal contact. Lithium floats v. high in the water, and only areas of contact generate heat. Cesium sinks like a rock.
2) Cesium boils a lot easier than lithium.
3) Ill bet, but dont know, that Cs has a much lower surface tension. This means its far easier for cesium to get a standing wave on its surface that encloses an drop of water (I think causing the explosion). If the metal has a very high surface tension this cannot happen without much bigger drops.

Bottom line is, I've got to get the cameras closer to the action to work it out, and regrettably that's not going to happen for months.

I'm heading out on the road, and trading the roof of bricks and mortar for that of dark night and bright stars.
:-)

The guys doing the rubidium are University of Nottingham.
http://www.youtube.com/user/periodicvideos

Category:

Education

Tags:

• brainiac
• alkali
• metals
• cesium
• rubidium
• potassium
• sodium
• lithium
• FAKE
• faking
• it
• explosives
• reacting
• with
• water
• boom
• explosion
• detonation
• chemistry
• chemist
• university
• of
• nottingham
• periodicvideos
• thunderf00t
• educational

[Lollocide]

I can't really get that worked up, its fucking Brainac, the show where they had people eating hot curries and then consuming various drinks to 'prove' their ability to deaden the taste of hotness. Or blowing up caravans. Or seeing if the 'tick-tacker' thing on a bike makes it go faster.

Saying Brainac has bad science is like saying the sun is hot.

[LozzaWayne]

Ahhh my childhood has been ruined... :'(

[sinister1110]

@An0nym0usPers0n123 No you're missing the point. Science is very cool and you can get some very large booms mixing chemicals... You just have to watch out for fakes in the science world. Don't take it as you see it, ask questions

[An0nym0usPers0n123]

i thought science was boring, i saw brainiac and thought it was cool, saw this and now know it is boring, :/

[TheDave]

I'm glad you covered this. I saw it on TV and it well fucked me off. I remember the days of OU tea time programming. That was good. This is just brain rotting unscientific sun reader bullshit.

[MrZmglm]

hmmmm i think im a bit late but u didnt mention that the lithium wins because it would need less energy to do all that compared to the Caesium. so the total Energy released by lithium will be represented by a smaller number (minus) so the greatest energy output ( absolute value wins :D) ( just in case people saying that the total sum for Caesium was bigger so it must be the winner)

[AlliTheSnowWolf]

Damn! I got into chem to blow shit up but this is just disappointing

[SgtTwinkleToes]

@LozzaWayne What do you mean ruined? Big explosions and boobs are more fun to watch than real caesium in water. :P

[b0b0maj0]

Ah first year Chemistry, I'd almost forgotten it. Thought it was a trick question, that Cs mass was lower in moles but I didn't know that Li would be correct with the same molar ratio.

[ParanoidAndroid15]

My university professor showed this to my class of 200, and who knows how many other classes. The next day, some one posted a link to this video on our class website. That both confirmed Thunderf00t's claim that this myth is widespread in universities, and showed me that the chemistry joke cat links I posted on our website under the name "Useful Chem Info" were not anonymous, like I thought they were.

[TrollAndStuff]

Dude Bill Nye is legit man... This brainiac guy is a retard... not a science guy... maaannnnn..... wtf