EvaporationandCooling
Whydoyousweat?
Howcanyoumakeathermometercooldown
belowroomtemperature?(Tryitout.Whatisthe
minimumtemperatureyoucanachieve?)
Nowtryatechniquetheteacherwillshowyouusingethanol.Record
theminimumtemperatureyoucanachieveusingthistechnique.
Whydoesanursewipeyourskinwithethanolwhentheygiveyouan
injection?
Explainingthecoolingeffectofevaporationusingparticles
Doyouthinkyoucanexplainwhyevaporationcausescoolingusing
particletheory?Herearesomeideastohelpyou.
1) Evaporationinvolvesaliquidchangingintoagas(i.e.achange
ofstate).
2) Changingfromaliquidtoagasinvolvedputtingenergyintothe
liquid.
3) Notallparticlesintheliquidmoveatthesamespeed.They
havedifferentkineticenergies.
4) Onlytheparticleswhicharemovingfastest(i.e.withthemost
kineticenergy)canovercometheforcesofattractionbetween
particlesintheliquidandescapetheliquidsurface.
5) Thetemperatureofaliquidisrelatedtothemeankinetic
energyofitsparticles.
©2016flippedaroundphysics.com
Drawaparticlediagramshowingevaporationfromthe
surfaceofaliquid.
What3factorsaffecttherateofevaporationfromaliquid?
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©2016flippedaroundphysics.com