OneMondaymorning,Paulandhisclassmateswereinsciencelaboratoryfortheirpracticalchemistrylesson.Thestudentsweregoingtoworkinpairstodoanexperiment.Beforetheybegan,theteachergavethemthisdescriptionofthedifferentstagesoftheexperiment.
Stage1:Preparetheequipment:atesttube,acrucible,aBunsenburnerandtongs.
Stage2:Weigh5gramsofbakingsoda(sodiumbicarbonate)andputitinacrucible.
Stage3:Heat10mlofhydrochloricacid(盐酸)inatesttube.
Stage4:Pourthewarmacidontothebakingsodaandcontinuetoheatthemixture.
Result:Theacidreactswiththebicarbonate（碳酸氢盐）toformwater,carbondioxidegasandsalt.Thehotterthemixture,thequickerthereaction.Continuetoheatthemixtureuntilthewaterevaporates,leavingthesaltinthecrucible.
Paulandhispartnerfollowedtheinstructionsandsetuptheirequipment.Paulwenttothecupboardtogetabottleofhydrochloricacid.Hefoundthattherewasonlyonebottleinthecupboardsohetookthat.TherewasnolabelonthebottleandPauldidn’tcheckwiththeteacherifitwastherightsolution.
Hemeasuredtheliquidandpoureditintoatesttube.Usingtongstoholdthetesttube,heheateditovertheBunsenburner.That’swhenthingsstartedtogowrong.Theliquidinthetesttubewasnothydrochloricacid.Whenitwasheated,itformedathickcloudofwhitegas.Soontheroomwasfullofthisstrongsmellingwhitegas.
Allthestudentsstartedcoughingandtheireyeshurt.Theteacherimmediatelyopenedthewindowsandorderedthestudentstoleavethelaboratoryatonce.Sherealizedthattheliquidwasacrylamide(丙烯酰胺)andthatitispoisonous.
Fortunately,nobodywasinjuredintheincident.However,ittaughtthestudentsandtheteacheragoodlesson.
小题1:Whatlessondidtheincidentteachthestudentsandtheteacher?