bbc化学史2字幕(2).doc

1、In , a wild-haired Russianchemist had an extraordinary vision.Hed been struggling witha mysterythat had perplexedscientists for generations.And for the very first time, hedglimpsed natures building blocks,the elements,arranged in their natural order.His name was Dmitri Mendeleev,and he was on the br

2、ink of crackingthe secret code of the Cosmos,what was to become one of mansmost beautiful creations,the Periodic Table of Elements.This is the story of those elements,the building blocks that make upthe universe.the remarkable taleof their discovery,and how they fit together, revealshow the modern w

3、orld was made.My names Jim Al-Khalili.And ever since I started studyingthe mysteries of matter,Ive been fascinated bychemistrys explosive history.Ho-ho! Brilliant!Ive discovered someexciting elements.Thats fantastic!and Ive seen how chemistrywas forgedin the furnaces of the alchemists.Now Im going t

4、o continuemy journey.Ill take up the questof the chemical pioneers.Well, my arms burning up.as they struggled to make senseof elemental chaosand conquerour fundamental fear of disorder.Could there be a grand planunderlying the elements?Ill take part in somevolatile experiments.Now were going to drop

5、in the potassium.Wow, look at that! Wahey!and witness somefiery reactions.And Ill find out how the hiddenorder of the natural worldwas revealed in all its glory -the order of the elements.As a nuclear physicist,Ive spent a lifetime studyingthe sub-atomic world,the basic building blocksof matter.But

6、to do that, I need to understandthe ingredients of OUR world.the elements.Our planet was createdfrom just elements.The ground we walk on, the air thatwe breathe, the stars we gaze at,even us.Our bodies areentirely made of elements.We now know the name and numberof every naturally-occurringelement in

7、 existence.But years ago,those elements were only justbeginning to give up their secrets.At the beginningof the th century,only had been discovered,from liquid mercuryto dazzling magnesium.and volatile iodine.Scientists had no idea how many morethey might find,or whether therecould be an infinite nu

8、mber.But the big question was,how did they fit together?Were they random stars,or was the elemental world born oforder and logic?Solving the puzzle would proveto be a daunting challenge.And the first glimmerings of ananswer came from an unlikely source.John Daltonwas an intelligent, modest man,and h

9、e had onevery British passion - the weather.He was born herein the Lake District in .He was so clever, thatas a young boy, just years old,he was already teaching other kidsat a school that he set up.Walking home, he loved watchingthe weather systemssweeping across the fells.He was so obsessed that h

10、e kepta meteorological diary for years,and every single day,come rain or shine,he entered his preciseobservations - , of them.Dalton was a quiet,retiring man with modest habits.He was a lifelong bachelor, with notmuch in the way of a social life.His only recreationwas a game of bowls once a week,eve

11、ry Thursday afternoon.He was certainlya creature of habit,and he might sound a bit dull.But actually, Dalton wasan avid reader and a deep thinker.Underneath his mild-manneredexterior,his head was teemingwith radical ideas.Now scientists had recentlydiscovered something very importantabout the way el

12、ements combineto form compounds.When they do so, they always combinein the same proportions.Dalton would have known thattable salt, sodium chloride,is always made up of one partsodium and one part chlorine.So it doesnt matter whether thesalt comes from Salt Lake Cityor Siberia, its always in the sam

13、eproportion by weight, every time.Dalton reckoned for this to happen,each element had to be made upof its own unique building blocks,what he called“ultimate particles“, atoms.It was a blinding illumination,completely left field.Everything, he suggested,the entire universe,was made up of infinitesima

14、llysmall particles.The Greeks had hit on the ideaof the atom , years earlier,but abandoned it.Now, Dalton took up the batonwith his own theory of matter.What Dalton was describingwas revolutionary.He had struck on the foundationsof atomic theory,foreshadowing research that wouldntbe proved until a c

15、entury later.He proposed that there are as manykinds of atomsas there are elements.And just as each elementis different,so each elements atom hasa different weight -a unique atomic weight.Every element has its own signatureatomic weight,whether it be a solid,a liquid, or even a gas.These three ballo

16、ons are eachfilled with a different gas.Now they are roughlythe same size,so they should each haveabout the same number of atoms in.Dalton reckoned that differentatoms have different atomic weights.So these three balloons shouldeach weigh different amounts.So this red balloonis filled with helium ga

17、s.And if I release it,it floats.Helium is very light.This second balloonis filled with argon gas.And if I release it,it sinks slowly.Argon is heavier than helium.The third balloon is filled withkrypton gas. And if I let it go,it falls like a stone.So Dalton was on the right lines -different atoms of

18、 differentelements have different weights.Based on this theory,and working completely alone,Dalton made oneof the first attemptsto impose some orderon the unruly world of the elements.This wonderfully mystical set ofsymbols is Daltons line-upof the elements arranged by weight.Now there are some elem

19、ents herethat I dont even recognise,but he does startwith hydrogen at one.Then you go down to oxygen at seven,and all the way down to mercuryat .As it turned out, Dalton didntget all of his weights right.But he had madea huge theoretical leapworking purely from his minds eye.Two hundred years ago,Jo

20、hn Dalton was usinghis imagination as a microscope.But today, we have the technology tosee the contours of individual atomswith this scanningtunnelling microscope.Its not like a normal microscopebecause it doesnt use light.Atoms are less than onemillionth of a millimetre across,which is smaller than

21、 the wavelengthof visible light.This microscope uses electronsto scan across the surfaceof materials,picking out individual atoms.The images it produces are striking.These are atoms of shining silicon.These are carbon atoms.This is what gold atoms look like.And these are atoms of copper.Copper is a

22、lustrous metal,essential for life.It fuelled the move out ofthe Stone Age into the Bronze Age.Copper nuggets can be foundon the earths surface,but it usually needsto be extracted from ores.And copper compounds runin the veins of some animals.The blood of the octopus is blue,along with snails, and sp

23、iders.John Daltons ideain the early s,that elements had differentatomic weights,was dismissed by many scientists.But one man believed in him -Swedish chemistJons Jakob Berzelius.Berzelius was obsessed with imposingsome kind of order on the elements.He was convinced that knowing moreabout the weight

24、of each elementwas somehow vitally important.And when heheard about Daltons theory,he came up with an ambitious plan.It was a gargantuan task.In fact, it seems almost mad.This lone Swedish chemist set outto measure precisely the atomicweight of every single element,and this without a shred of prooft

25、hat atoms even existed.But before Berzelius could start,he was going to have to purify,dilute, filtereach element incredibly accurately.And that was farfrom straightforward.At the time,very little of the crucialchemical apparatusneeded for work of this precisionhad even been invented.But that wasnt

26、going to stopa man like Berzelius.He was on a mission.So Berzelius set out tomake his own lab equipment.Ah, Liam. Hi, Jim. Nice to meet you.Come through to the hotshop.Liam Reeves,a professional glassblowerat the Royal College of Art willshow me how Berzelius did it.Glassblowing is physicallydemandi

27、ng,and calls for working atpunishingly high temperatures.Berzeliusmust have been very dedicated.Im getting the glass out now,which is at about, degrees centigrade.Im using a wooden blockjust to cool and shape the glass.What is it youre making?It will be a round-bottomed flask,which would have been p

28、art of thebasic chemistry equipmentthat Berzelius would have used. NowIm going to introduce some air,which Ill trap in the pipeand the heat makes expand.Wow! How hard would it have beenfor Berzelius to learn to do this?They say it takes years tokind of.to really master glass.He was a very skilled gl

29、assblowerfrom the evidencethat Ive seen of his work.What he was making washigh-precision apparatus,so that must have made itfar more difficultthan your average vase or tumbler.From the pictures that Ive seen,Ive got no idea how he made it.Really? Yeah. No idea. So Im justmaking the top of the bottle

30、 now.Right, so thats a basicround-bottomed flaskvery much like onethat Berzelius would have made.Glassblowing isnt somethingtheoretical physicists like menormally do.But I want to find out for myselfjust how hard it is tomaster this new skill.OK, just turn a little bit slower.Come back ever so sligh

31、tly.Ah! Well, my arms burning up.Ill shield you, actually.Oh, thats better.Its going rather well.SNAP!Oh-h!Oh, well.That just goes to show howdifficult this is.So it does take years to do.I think you would havemanaged it in seven or eight.Theres my flaskdying slowly, melting away.I mean, it just goe

32、s to provehow incredibly talentedBerzelius was - he wasnt makingsomething basic like this,he was makingsome really intricate stuff.And although he was searching forelemental order, there was a bonus.The great thing, you see,about Berzelius was that the skillshe learned as a glassblowerled him to an

33、incredible discovery.In , he discovereda new element,because he found that one of theconstituents of glass was silicon.Silicon is a semi-metallic element.found within some meteorites.Closer to home, its under your feet.The earths crust is madeprimarily of silicate minerals.Silicon is its second most

34、abundant element, after oxygen.Its mostly found in natureas sand or quartz.Its man-made compoundscan be heat resistant,water resistant and non-stick.But silicons ultimate achievementhas to be the silicon chip,shrinking computersfrom room size to palm size.Silicon was the last of fourelements that Be

35、rzelius isolated,along with thorium,cerium, and selenium.He then spent the next decadeof his lifemeasuring atomic weight afteratomic weight after atomic weightin an obsessive pursuit of logicin the face of the seemingly randomchaos of the natural world.Berzelius laboriously studiedover , chemical co

36、mpoundswith staggering dedication.He weighed, he measured and heagonised over the tiniest detailuntil hed found out the relativeweights of different elements.Some of his resultswere remarkably accurate.His weight for chlorine, a gas,got to within a fifthof a per cent of what we know today.But by the

37、 time Berzeliusproduced his results,other scientists had startedmeasuring atomic weightsand come up with completelydifferent answers.Now they were pittedagainst each other,perhaps fuelled by an innatedesire to find meaning in disorder.Berzeliuss questfor order was contagious.Scientists began looking

38、 forpatterns everywhere.One of these was German chemistJohann Wolfgang Dobereiner.He believed that the answerlay not with atomic weightsbut with the elementschemical properties and reactions.Dr Andrea Sella has studiedDobereiners workon chemical groups.What Dobereiner had really spottedwas that if y

39、ou consideredall the elements that were known tothat time,you could often pick out three -“triads“, as he called them,which had very, very closelyrelated chemical properties.And as an example, we have herethe alkali metals.And Im going to take the firstand the lightest of them, lithium.And we have t

40、o store these under oilbecause they tend to react with airand moisture. So here goes lithium.Pop it in.Oh, look, fizzing away, yeah.You can see it fizzing.And the fizzing is hydrogen,flammable air, being released.And at the same time,its leaving a pink trail.Weve put a bit of indicatorin there, whic

41、h is telling usthat whats left behind is caustic.Its actually makingan alkaline solution.Im breathing in some caustic soda!Well, youre getting a littlebit of steam coming off,and the reactionis very, very exothermic.In other words,the temperature rises a lot,and the metal has actually melted.The sec

42、ond metal in this triadwas sodium.And when we drop the sodium in.Whoa!Oh, look at that, flashes of light!Orange sparks. And those orangesparks are the same colouras what you get in streetlights.Streetlights have sodium in them.Right.Well, the third one in the seriesis potassium.The potassiumturns ou

43、t to be the tiger.And we may need to stand back.Look at those flashes. Wow!And you can see that lilac flame.And one could really see trendsin these triads.Theyre all doing thesame thing, arent they? Yes.The fizzing is telling usthat hydrogen is coming off.Were gettingthe alkali being formed.But the

44、lithium is relatively tame,the sodium was more excitable,the potassium starts getting scary.Dobereiner realised that theseelements must be a familybecause they reactedin a similar way.Here was the hint of a pattern.But it only worked ona few of the elements.It got scientists no furtherthan atomic we

45、ights had done.The bigger picture, the universalorder of all the elements,was still hard to see.And that wouldnt change untila breakthroughby one of greatest mindsin th-century science.In , in the far west of Siberia,a massive fire destroyed a factory.The factory managerfaced destitution.She was a w

46、idow, Maria Mendeleeva,and she made a remarkable sacrificefor her precociously intelligent son,-year-old Dmitri Mendeleev.Maria was well awareof her sons intelligence,and with a steely determinationshe set out to get him an education.So, together with Dmitri, she setoff on a ,-mile journeyfrom Siber

47、ia to St Petersburg.And incredibly, they walked a goodpart of that journey.Im following in their footstepsto St Petersburg,then the capitalof the Russian empire.After their arduous journey acrossthe Russian steppes,mother and sonfinally arrived at St Petersburg.Maria Mendeleevahad got what she wante

48、d,but the effort destroyed her.She died ten weeks later.The story goes that herlast words to her son were -“Refrain from illusions andseek divine and scientific truth.“And young Mendeleev promised to obey.He studied day and nightto fulfil his mothers dreamand became the most brilliantchemistry stude

49、nt of his generation.Chemistry had come a long way sincethe Greeks idea of four elements -earth, air, fire and water.But there was still no orderto the elementsthat had so far been discovered.Now the search for a pattern grippedsome of the best minds in science.But no-one could agreehow to find it.Mendeleev was still a studentwhen he attendedthe worlds first ever internationalchemistry conference.The worlds chemists had gatheredto settle the disputethat was holding back their subject,the con