Kinetic theory says that molecules are in constant motion. Perfume molecules moving across the room are evidence of this.

Transcription

1 Chaptr 13- Th Stats f Mattr Gass- indfinit vum and shap, w dnsity. Liquids- dfinit vum, indfinit shap, and high dnsity. Sids- dfinit vum and shap, high dnsity Sids and iquids hav high dnsitis bcaus thir mcus ar cs tgthr. Kintic Thry Kintic thry says that mcus ar in cnstant mtin. Prfum mcus mving acrss th rm ar vidnc f this. Th Kintic Thry f Gass Maks thr dscriptins f gas partics 1. A gas is cmpsd f partics mcus r atms Cnsidrd t b hard sphrs far nugh apart that w can ignr thir vum. Btwn th mcus is mpty spac. 2. Th partics ar in cnstant randm mtin. Mv in straight ins unti thy bunc ff ach thr r th was. 3. A cisins ar prfcty astic Th Avrag spd f an xygn mcu is 1656 km/hr at 20ºC Th mcus dn t trav vry far withut hitting ach thr s thy mv in randm dirctins. Kintic Enrgy and Tmpratur Tmpratur is a masur f th Avrag kintic nrgy f th mcus f a substanc. Highr tmpratur fastr mcus. At absut zr (0 K) a mcuar mtin wud stp. Pag 1 1

2 % f M c u s Kintic Enrgy High tmp. Lw tmp. % f M c u s Kintic Enrgy High tmp. Lw tmp. Fw mcus hav vry high kintic nrgy % f M c u s Kintic Enrgy High tmp. Lw tmp. Avrag kintic nrgis ar tmpraturs Tmpratur Th avrag kintic nrgy is dircty prprtina t th tmpratur in Kvin If yu dub th tmpratur (in Kvin) yu dub th avrag kintic nrgy. If yu chang th tmpratur frm 300 K t 600 K th kintic nrgy dubs. Tmpratur If yu chang th tmpratur frm 300ºC t 600ºC th Kintic nrgy dsn t dub. 873 K is nt twic 573 K Prssur Prssur is th rsut f cisins f th mcus with th sids f a cntainr. A vacuum is cmpty mpty spac - it has n prssur. Prssur is masurd in units f atmsphrs (atm). It is masurd with a dvic cad a barmtr. Pag 2 2

3 1 atm Prssur Barmtr At n atmsphr prssur a cumn f mrcury 760 mm high. Cumn f Mrcury Dish f Mrcury 1 atm Prssur 760 mm Barmtr At n atmsphr prssur a cumn f mrcury 760 mm high. A scnd unit f prssur is mm Hg 1 atm = 760 mm Hg Third unit is th Pasca 1 atm = kpa kipascas kpa Prssur units 1 atm = 760 mm Hg = kpa Can mak cnvrsin factrs frm ths Cnvrt 1 atm = 760 mm Hg = kpa 743 mm Hg t atm 895 kpa t mm Hg Sam KE diffrnt spd Mass affcts kintic nrgy. Lss mass, ss kintic nrgy at th sam spd Th smar partics must hav a gratr spd t hav th sam kintic nrgy. Sam tmpratur, smar partics mv fastr Liquids Partics ar in mtin. Tnds t pu thm apart Attractiv frcs btwn mcus kp thm cs tgthr. Ths ar cad intrmcuar frcs. Intr = btwn Mcuar = mcus Pag 3 3

4 Braking intrmcuar frcs. Vaprizatin - th chang frm a iquid t a gas bw its biing pint. Evapratin - vaprizatin f an uncntaind iquid ( n id n th btt ). Evapratin Mcus at th surfac brak away and bcm gas. Ony ths with nugh KE scap Evapratin is a cing prcss. It rquirs nrgy. Cndnsatin Chang frm gas t iquid Mcus stick tgthr Rass nrgy. Cndnsatin Achivs a dynamic quiibrium with vaprizatin in a csd systm. What is a csd systm? A csd systm mans mattr can t g in r ut. (put a crk in it) What th hck is a dynamic quiibrium? Dynamic quiibrium Dynamic quiibrium Whn first sad th mcus graduay scap th surfac f th iquid Whn first sad th mcus graduay scap th surfac f th iquid As th mcus buid up abv th iquid sm cndns back t a iquid. Pag 4 4

5 Dynamic quiibrium As tim gs by th rat f vaprizatin rmains cnstant but th rat f cndnsatin incrass bcaus thr ar mr mcus t cndns. Equiibrium is rachd whn Dynamic quiibrium Rat f Vaprizatin = Rat f Cndnsatin Mcus ar cnstanty changing phas Dynamic Th amunt f iquid and vapr rmains cnstant Equiibrium Vapr Prssur In a csd cntainr th gas mcus wi caus prssur. Th prssur at quiibrium is cad vapr prssur Diffrnt cmpunds hav diffrnt vapr prssurs bcaus f diffrnt intrmcuar frcs Strngr frcs, wr vapr prssur Vapr Prssur At highr tmpratur thr ar mr gas mcus Mr hav th nrgy t scap Highr vapr prssur Vaprizatin Vaprizatin rquirs hat. Enrgy is rquird t vrcm intrmcuar frcs Absrbing hat cs Highst kintic nrgy avs Avrag drps Why w swat. % f M c u s T 1 Kintic nrgy Enrgy ndd t vrcm intrmcuar frcs Pag 5 5

6 % f M c u s At highr tmpratur mr mcus hav nugh nrgy Highr vapr prssur. Kintic nrgy T 2 Biing Making bubbs f gas Frcs iquid v t ris Must push against air prssur n th iquid. Biing Changing th Biing Pint A iquid bis whn th vapr prssur = th xtrna prssur Tmpratur is cad th biing pint Nrma Biing pint is th tmpratur a substanc bis at 1 atm prssur. Th tmpratur f a iquid can nvr ris abv it s biing pint Enrgy gs int braking frcs, nt mving fastr. Lwr th prssur (ging up int th muntains). Lwr xtrna prssur rquirs wr vapr prssur. Easir t mak bubbs Lwr vapr prssur mans wr biing pint. Fd cks swr. Changing th Biing Pint Rais th xtrna prssur (Us a prssur ckr) Raiss th vapr prssur ndd. Hardr t mak bubbs Raiss th biing pint. Fd cks fastr. Diffrnt Biing pints Diffrnt substancs bi at diffrnt tmpraturs bcaus thy hav diffrnt intrmcuar frcs Wak frcs- wr biing pint Diffrnt vapr prssurs Lw vapr prssur high biing pint Pag 6 6

7 Sids Intrmcuar frcs ar strng Mcus sti mv Can ny vibrat and rvv in pac. Partics ar ckd in pac - dn t fw. Mting pint is th tmpratur whr a sid turns int a iquid. Th mting pint is th sam as th frzing pint. Sids Whn hatd th partics vibrat mr rapidy unti thy shak thmsvs fr f ach thr. As thy ar hatd th tmpratur dsn t chang. Th nrgy gs int braking bnds, nt incrasing mtin Mv diffrnty, nt fastr. Sids Mcuar sids hav wak intrmcuar frcs s a w mp. Par mcus highr mp than nnpar Hydrgn bnding highr sti Inic sids hav strngr intrmcuar frcs s vn high mp. Crystas A rguar rpating thr dimnsina arrangmnt f atms in a sid. Mst sids ar crystas. Brak at crtain angs Cubic Bdy-Cntrd Cubic Pag 7 7

8 Fac-Cntrd Cubic Atrps Whn n cmpund has tw r mr crysta structurs, thy ar cad atrps. Graphit, diamnd and st ar a carbn Nw carbn structurs- Furns- pattrn n sccr ba Carbn nantubs Amrphus sids ack an rdry intrna structur. Think f thm as supr-cd iquids. Gasss ar n typ. Rigid but acking structur D nt mt- just graduay gt sftr. Shattr at randm angs Phas Changs Rquir nrgy Subimatin Mting Vaprizatin Mting Vaprizatin Sid Liquid Gas Sid Liquid Gas Frzing Cndnsatin Frzing Cndnsatin Cndnsatin Ras nrgy Pag 8 8

9 Tmpratur and Phas Chang Th tmpratur dsn t chang during a phas chang. If yu hav a mixtur f ic and watr, th tmpratur is 0ºC At 1 atm, biing watr is 100ºC Yu can t gt th tmpratur highr unti it bis Hating Curv A graph f Enrgy vrsus tmpratur Hating Curv fr Watr Watr Watr and Stam Stam Watr 0 Ic and Ic ca/g Phas Diagram Graph f Prssur vrsus tmpratur fr a cmpund. Draw ins whr th phas changs. Prssur Sid 1 Atm B A Liquid C B A C Prssur Sid Trip Pint Liquid Critica Pint Gas Gas Tmpratur Tmpratur Pag 9 9

10 Prssur This is th phas diagram fr watr. Th dnsity f iquid watr is highr Sid than sid watr. Liquid Prssur This is th phas diagram fr CO 2 Th sid is mr dns than th iquid Th sid subims at 1 atm. Sid Liquid Gas 1 Atm Gas Tmpratur Tmpratur Pag 10 10