大学英语六级阅读晨读文章分享 英语四六级报名

下面小编跟大家一起了解大学英语六级阅读晨读美文分享，希望对大家有所帮助。

Tounderstandtheemulsifyingprocess,wemustfirstacceptthescientificprinciplethatoilandwaterdonotnaturallymix.Quiteliterally,theyfindeachother'spresencerepulsive.Agoodillustrationofthisaversionishomemadeoilandvinegarsaladdressing.Whenyoushakeorbeatyoursaladdressing,youdomorethandispersetheoilthroughoutthevinegar:youalsobreakdowntheoilintodropletsminuteenoughtoremaintemporarilysuspendedinthevinegar(whichfromnowonwewillcallwater,becausethattartcondimentisineffectmainlywater).Thesecondyoustopagitatingthedressing,

theoildropletsstarttocombineintounitstoolargetobesuspendedinthewater,andthusslithertheirwayupward,separatingfromthewaterintheprocess.Theoilrisestothetopandthewatersinksbecauseoilhasalowerspecificdensitythanwater.Ifyouwantastableemulsion,youneedanemulsifyingagentwhichpreventstheoildropletsfromcombiningintolargerunits.

Emulsifyingagentsoccurnaturallyinmanyanimalsubstancesincludingeggyolksandmilk.Anemulsifyingagenthelpstokeeptheoilparticlesfromcombininginthreebasicways.First,theagentcoatstheoil,servingasaphysicalbarrierbetweenthedroplets.Second,itreducesthewater'ssurfacetension,which,inturn,reducesthewater'sabilitytorepulseoil.Third,theagentgivesthesurfacesoftheoildropletsidenticalelectricalcharges;sincelikechargesrepeleachotherthedropletsrepeleachother.