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Chng 4. LIN KT CC HNGNG T.CU TO V TNH CHT

4.1. i cng vtinh th4.1.1. c trng vcu trc

a. Khi nim

Nu githit cc phn tcu to nn vt cht l cc nguyn t, ion hoc phn t,th tinh thl trng thi m , cc phn tsp xp trong khng gian to nn mt quylut no . Vmt hnh hc, cc phn tcu to c xem nhnhng cht im, quylut ca nhng cht im ny l tnh i xng v hon ton trong khng gian tinh th.Do vy, tinh ththng nhn mt hnh thi nht nh di dng mt a din no .

Khi lm ngui t tmt dung dch bo ha hay mt cht lng, chuyn ngnhit ca cc ht gim, nhng phn t, nguyn thay ion tp hp li v phn b, spxp thnh mng li khng gian vi mt cu trc xc nh. Khi ta c mt tinh th,hay qu trnh ny gi l qu trnh kt tinh.

Trong thc t, cc cht rn tinh thc to thnh t nhiu tinh th rt nh(khong 10 20 m) nh hng khc nhau. Cc cht rn nhvy gi l a tinh th.Vi nhng tinh thto nn cht rn nhmt tinh thduy nht c gi l n tinh th.

b. Tnh cht

- Tnh bt ng hng ca tinh th: Trong tinh th, cc n v cu trc lin kt vi

nhau bng nhng lin kt ha hc v c phn bmt cch tun hon theo nhngquy lut nht nh to thnh mt mng li khng gian u n, mc d chng c thng hng vi mt vi tnh cht no .

V d: Tinh th mui n dng lp phng, ng hng v tnh quang hc,nhng dhng vnhiu tnh cht nh: tnh chc, tnh dn in,...

Tnh bt ng hng thhin chnhiu tnh cht vt l nhbn chc, skhc xnh sng, tnh dn nhit, tnh dn in, cng, tc ha tan,... c gi trkhc nhau theo nhng hng khc nhau.

- Lc ht gia cc ht (nguyn t, phn t, ion) trong mi trng thi tinh th lun l

lc ht tnh in.V dtinh thcu to tcc phn ttrung ha in th snh hng tng i

gia chng c thlin quan ti sc mt ca lng cc in trong ht.

- Tnh nh vnht nh trong vng khng gian tinh th: nhit thng, cc phnt dao ng quanh v tr cn bng vi mt bin nht nh, nhng nhit cngtng, bin dao ng cng ln.

- Mi tinh thtrong qu trnh kt tinh phthuc vo cc yu tsau:

+ Tnh i xng: Thng thng mt cht c thnh phn ha hc cng n gin

th mng li tinh thc tnh i xng cng cao.+ Tlgia bn knh cc loi ht trong mng li.

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+ Lc tng tc gia cc ht (bao gm mnh, tnh nh hng ca cc milin kt gia cc ht).

+ iu kin bn ngoi (nhit , p sut,...), i khi cng nh hng n cutrc ca tinh th.

4.1.2. Cc htinh th

Mng li tinh thc thcoi nhc cu to bi nhng hnh hp m nh lcc cu tng nht (nguyn t, phn t, ion).

Hnh 21. Mng li tinh th

Mt hnh hp c bit gi l tbo sng (hay mng cs) c xc nhbng skt hp mt siu kin sau y:

- Tbo sng phi c tnh i xng cao.

- Sgc vung phi nhiu nht.

- Thtch phi nhnht.

Trong tinh thhc, hthng ta c chn lm 3 trc i qua mt im mngv trng vi phng ca 3 cnh ca t bo s ng. Cc trc a, b, c, cc gc

,,, cng nhcc cnh a0, b0, c0ca tbo sng (c sdng lm n vding vi trc a, b, c) c quy nh thng nht nhsau:

Hnh 22. Tbo sng v htrc ta qui c

Cc cnh a0, b0, c0, cc gc ,,, c gi l hng smng.

C 7 h tinh th: H tam t, h n t, h trc thoi, h tam phng, h tphng, hlc phng, hlp phng.

4.1.3. Cc mng li Brave (Bravais)

Trong mng Brave c la chn tun theo nguyn tc ca mng c s,ngha l tnh i xng ca n c ginguyn nhton mng, sgc vung nhiunht v thtch nhnht.

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Sau y l cc mng Brave:

Tam t n t Tgic

Trc giao Trc thoi

Lp phng Lc gic

Hnh 23. Mi bn mng Brave

Trong mng Brave c tnh i xng cao nht ca htinh th. Tuy nhin tinh ththng c tnh i xng thp hn. Trong mng, ngoi cc yu t i xng thngthng, xut hin hng lot yu ti xng c trng cho mng khng gian. Ngoi sa dng , trong cu trc tinh thcn bt gp nhiu hin tng thhin chv syu ti xng cng loi song song.

4.2.Tinh thion

4.2.1. Lin kt ha hc trong tinh thiona. Khi qut m hnh ion v shnh thnh tinh thion

* M hnh ion c hnh thnh trn cs

- Tinh thca cc cht m nt mng ca chng c hnh thnh bi nhng cation vanion hnh cu vi mt bn knh xc nh.

- Lc tng tc gia cc ion trn nt mng l lc ht tnh in khng nh hng.

* Shnh thnh tinh thion

Trong nhng tinh thion, cc nguyn tbin thnh cc ion dng hay m xenln nhau, v sckt ny c c l do sht tnh in gy nn. Khi cc nt li

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l do cc ion dng hoc m ln lt chim gi, cc ion ny lin kt vi nhau bnglin kt ion.

V lin kt ion l loi lin kt bn khng nh hng, khng bo ho, nn mngli ion c c im:

+ C bn cao, cng cao.

+ Tun theo nguyn l sp xp c kht nht.

+ Tnh dn in, dn nhit km.

V d:

Trong mng tinh thion NaCl c sphi tr bng 6. mng csc dng hnhlp phng. Cc ion Na+ nm tm v trung im cc cnh hnh lp phng, cc ionCl-nh v im gia cc mt hnh lp phng.

Nu xem cc ion cc nt mng nhnhng qucu tip xc vi nhau th ivi mi ion ta stm thy mt bn knh xc nh v khng i, khi ta chuyn ttrng

thi cht ny sang hp cht khc.Cc cation c bn knh nhhn bn knh ca nguyn tkim loi tng ng.

Cc cation ni chung c bn knh ion nhhn so vi cc anion.

Cc gi trca bn knh theo angstrom (A0):

Cl- 1,81 Na+ 0,95 Na 1,92

I- 2,16 K+ 1,33 K 2,38

b. Nng lng mng li hp cht ionNng lng mng li ca mt hp cht ion kt tinh l nng lng c gii

phng trong qu trnh hnh thnh mt mol phn ttinh thtnhng ion ring r(khiu l U, thng quy c c du tr).

V d: NaCl. Uml = - 766kJ/mol.

Nng lng mng li quyt nh bn, ha tan v nhiu tnh cht khcca tinh th.

Cng thc thc nghim xc nh nng lng mng li theo Booc Lan(Born v Land):

)1

1(22

nr

eNAzUml =

n- hsy Booc, c xc nh ttinh thchu nn ca ion

Vi NaCl, n = 9,1;

LiF, n = 5,9;

NaBr, n = 9,5

N - sAvogaro

A - hng sMalung, phthuc cu trc mng li tinh th;

vi NaCl, A = 1,748.

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Cng thc gn ng xc nh nng lng mng li theo Kapustinxki:

ac

ac

mlrr

vzzU

+=

...5,1071 [kJ/mol]

zc, za- sin tch ca cation v anion.

rc, ra bn knh ca cation v anion tnh ta A0.

v - sion trong n vcng thc.

Vi CaCl2th = .3v

4.2.2. Cu trc ca tinh thion

Do tnh khng nh hng ca lc ht tnh in gia cc ion trong tinh thion,nn cu trc tinh thion vcn bn l do stng quan gia bn knh cation v anionquyt nh.

V d: Trong tinh thNaCl

Trong tinh th NaCl, mi loi ion to thnh mt mng li lp phng tmdin. Mi ion c bao quanh bi 6 ion khc du gn nht nm ti nh ca hnh bt

din u m tm l ion trn. Sphi tr l 6.

4.2.3. Tnh cht ca tinh thion

Tnh cht cc hp cht ion phn nhiu c quyt nh bi cu trc ca tinh thv lc tng tc gia cc ion trong tinh th.

Cc hp cht ion c rn, nhit nng chy, nhit si tng i cao, gin nnhit cng nhchu nn tng i nh. Yu tny l do lc tng tc tnhin gia cc ion tng i ln.

Hsgin nnhit cng phthuc vo nng lng mng li ion: Hsgin

n nhit cng ln khi in tch ca cc ion cng nhv khong cch gia cc ioncng ln.

V d, khong cch gia cc ion tng theo thtNaF, NaCl, NaBr, NaI, nn hsgin ncng tng theo thttrn.

Cc hp cht ion l nhng cht dn in trng thi nng chy: Cc tinh thion rn v dn hn, dn ca chng l do khi ion di chth lc y ca cc ion tchin cng du bt u thng lc lc ht gia cc ion khc du, v tinh thdbphv. V vy trng thi rn, cc ion khng c tnh dn in.

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Bng 4. Nhit nng chy cc tinh thion (0C)

CationAnion

Li+ Na+

F-

848 995

Cl- 610 800

Br- 550 750

I- 449 662

OH- 473 321

S2- - 1180

O2- 1570 -

2 220 283

Nhit nng chy cao, cho thy cc hp cht ion c nng lng ln.

4.3. Tinh thkim loi

4.3.1. Lin kt ha hc trong tinh thkim loi

a. M hnh kh electron ca ruv Loren (Drude, Lorentz)

Theo m hnh ny, cc electron c kh nng tch khi nguyn tv di ngtng i tdo trong nguyn tto thnh mt m kh electron. Stng tc giakh electron ny vi ion dng kim loi cc nt mng l nguyn nhn ca lc linkt kim loi.

Da trn m hnh ny, ta c thgii thch mt stnh cht vt l ca kim loinh: tnh dn nhit, dn in, tnh cng, khnng hp thv phn xnh sng,...

Tuy nhin vi m hnh trn, kh khn trong vic gii thch nhit dung ca kimloi.

J/(kg K) = 2.389x10-4kcal/(kg oC)1 kJ/(kg K) = 0.2389 kcal/(kg oC)

1 kcal/(kg oC) = 4,186.8 J/ (kg K)

Theo thuyt ng hc ca cht kh, trong tinh thkim loi, cc electron tdophi c phn ng gp vo nhit dung chung ca tinh thkim loi l 3/2R (R - hngs kh = 8,3144J/mol.K = 1,98 cal/mol.K). iu ny mu thun vi kt qu thcnghim l phn ng gp ca cc kh electron l khng ng k.

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Bng 5. Nhit dung cthca mt skim loi thng thng

Nhit dung ringca kim loi - cp

Nhit dung ringca kim loi - cpKim loi

(kJ/kg K) (kcal/kgoC)

Kim loi(kJ/kg K) (kcal/kg

oC)

K 0.75 0.180 Pt 0.13 0.032

Be 1.83 0.436 Cd 0.23 0.055

Al 0.91 0.22 Cr 0.46 0.11

Se 0.32 0.077 Co 0.42 0.1

Mg 1.05 0.243 Bi 0.13 0.03

Sb 0.21 0.05 Cd 0.23 0.055

Cu 0.39 0.092 Au 0.13 0.031

Mn 0.48 0.114 Fe 0.46 0.108

Hg 0.14 0.033 Pb 0.13 0.031

Mo 0.25 0.06 Ni 0.54 0.106

b. M hnh di nng lng

M hnh ny da trn csvelectron khng nh c(tc l electron chuynng trn cc MO chung ca ton phn t). Trn csny, thuyt MO thch hp trongvic m tlin kt kim loi.

Cc trng thi electron y cng c hnh dung nhcc trng thi electron khng nh c trong phn t benzen hay trong cc h electron khng nh ctrong phn tc hlin kt lin hp.

Hnh 24. Shnh thnh di nng lng ca MO khng nh c

Gii thch theo m hnh trn:

- i vi phn tc sthp ca N obitan nguyn tscho N/2 MO lin ktv N/2 MO phn lin kt vi cc mc nng lng ri rc, gin on.

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- Trong tinh thkim loi, snguyn tv cng ln, nn sAO cng v cngln. V vy, sthp cc AO ny cng cho mt sv cng ln cc MO, v nhthhiu cc mc nng lng sv cng nh. Khi sphn bmc nng lng gn nhlin tc v tp hp cc mc nng lng nm st nhau c gi l di nng lng.

- Khi hiu nng lng gia cc mc phn lin kt thp nht v cc mc lin kt

cao nht cng nhtrn nguyn ttrong tinh thkim loi th sxy ra sxen phccdi nng lng.

V d:

Hnh 25. Di nng lng i vi tinh thLi

4.3.2. Cu trc trong tinh thkim loi

Trong tinh thkim loi thng mi nguyn thay ion kim loi c bao bcbi 12 hay 8 nguyn tcng loi (sphi tr bng 8 hoc 12). Cc ion hoc nguyn tkim loi trong mng li lin kt vi nhau nhcc my electron tdo khng nh chv khng cnh vo mt nguyn tno.

Trong tinh th kim loi cc nguyn t kim loi nm cnh nhau nh myelectron ho tr xen phln nhau, nn mi electron ho trschu tc dng ng thiin trng ca nhiu nguyn t. V vy electron ho trc thchuyn tnguyn tny sang nguyn tkhc m khng cn tiu thnng lng. l nhng electron tdotrong tinh th.

Cc nguyn tkim loi c sp xp mt cch kht nht ng vi mt sphi trcc i. V cc nguyn tkim loi c coi l hnh cu, nn cch sp xp ny ccoi l cch sp xp mt qucu kht nht.

Ba kiu mng tinh thca hu ht kim loi l: lc phng, lp phng tm dinv lp phng tm khi.

Lc phng, Lp phng tm din Lp phng tm khi.

Hnh 26. Cc kiu mng tinh thkim loi

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Hnh 27. Mt sdng cu trc tinh thtrng thi cbn

Bng 6. Kin trc tinh thca cc kim loi:

Li

3

Be

2

K

3

Ca

1,2

Sc

1,2

Ti

2,3

V

3

Cr

3

Mn

-

Fe

1,3

Co

1,2

Ni

1,2

Cu

1

Zn

2

Rb

3

Sr

1

Y

2

Zr

2,3

Nb

3

Mo

2,3

Te

2

Ru

1,2

Rh

1

Pd

1

Ag

1

Cd

2

Cs

3

Ba

3

La

1,2

Hf

2,3

Ta

3

W

3

Re

2

Os

1,2

Ir

1

Pt

1

Au

1

Hg

-

Trong : S1- Chmng li lp phng tm din;

S2- Chmng li lc phng;

S3- Chmng li lp phng tm khi;

4.3.3. Tnh cht ca kim loi

Tinh thkim loi c nhng tnh cht c bit nh: khnng bin dng n hi,ddn in, dn nhit, nh kim,

Hnh 28. Sbin dng khng n hi ca kim loi

Gii thch:

- Khnng bin dng ca kim loi c gii thch bi tnh khng nh hng ca lclin kt v tnh ng nht ca cc cu t. Khi xy ra bin dng c strt ca cc mtli so vi nhau.

- Mc d trn cc MO bo ha, th schuyn ng ca electron khng tun theomt phng xc nh. Nhng theo m hnh di nng lng th trong mng tinh thkim

loi lun tn ti nhng MO tdo (khng c electron), c mc mng lng gn vi ccMO bo ha electron. Do , khi c stng tc ca in trng ngoi, cc electron

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dchuyn ln cc MO tdo v t c sdi chuyn electron theo phng ca intrng ngoi. l nguyn nhn ca tnh dn in ca kim loi.

- Kim loi c in trnh, in trkim loi l hquskhuch tn ca electron khigp ion dao ng.

- Kh nng bin dng ca kim loi cho php nhng nguyn t chim v tr mi m

khng lm t lin kt. Cng do nguyn nhn ny m kim loi in hnh c nhit nng chy thp.

4.4. Tinh thnguyn t

4.4.1. Lin kt ha hc trong tinh thnguyn t

Trong tinh thnguyn t, cc cu tl nhng nguyn t, lin kt vi nhau bnglin kt cng ha tr. V vy tinh thnguyn tcn c gi l tinh thcng ha tr.

V d: kim cng, than ch, Sn, Ge, BN, GaAs,...

Sphi tr ca nguyn t trong tinh thnguyn t thng c gi tr t1 8.

i vi n cht trng thi tinh th, sphi tr thng bng 8 trsthtca nhmnguyn t. iu ny c gii thch bi quy tc bt t. Khi , hin tthun livmt nng lng.

Bng 7. Chsphtr ca mt snguyn t

Sphi tr cc nguyn tcc nhmChu

k I II III IV V VI VII

2 Li 8 Be 12 B 5(7) C 4 N 1 O 1 F 1

3 Na 8 Mg 12 Al 12 Si 4 P 3 S 2 Cl 1

4 K 8 Ca 12 Ga 1 Ge 4 As 3 Se 2 Br 1

Sn (dng ): Thit xmdng bt; cn vi thit trng(dng ) c cu trchnh bt din.

Mt shp cht AB to thnh tinh thkiu nguyn t, khi tng sin tha trca A v B bng 8. Thomn iu kin ny c cc hp cht ca cc nguyn t thucnhm I v VII (nhCuCl); II v VI (nhZnS); III v V (nhBN) v IV (nhSiC).

Cn ch rng, nguyn tcc nguyn tnhm IA v mt phn IIA do c min thp, nn chng ddng ion ha to thnh tinh thion.

Nhiu cht c kh nng to thnh tinh th nguyn t nh cc lin kt cho -nhn, cc lin kt ny xut hin gia nhng nguyn tkhc nhau ca cc phn tring

bit khi cht chuyn sang trng thi rn. Chng hn vi BeF2:

F B e F B e F

F F

B e F B e F

F

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4.4.2. Cu trc mng li kim cng

Tinh thkim cng c cu trc tdin. Cc nguyn tcacbon nm tm vnh ca tdin u lin kt vi nhau bng lin kt cng ho tr. Khong cch C C

bng 1,54A0, khong cch ny bng khong cch C C ca hidrocacbon no. Cu trcny c lp li trong ton btinh thkim cng. V mi nguyn tcacbonlin kt

vi 4 nguyn tcacbon gn nht nn kim cng c rt nhiu tnh cht ring.

Cc lin kt C C trong tinh thkim cng

Hnh 29. Cu trc tinh thkim cng

Khi lng ringca kim cng l 3,52 g/cm

4.4.3. Tnh cht ca tinh thnguyn t

rn ln,

Nhit nng chy v nhit si cao, cng cao.

Chng l cht cch in hay bn dn.

Khng lun lun tun theo trit nguyn l sp xp c kht nht, v ccnguyn tphi sp xp ph hp vi phng lin kt.

4.4.4. Cht cch in, cht bn dn

Tnh dn in ca kim loi, cht bn dn v cht cch in u c thc giithch trn csm hnh di nng lng.

Hnh 30. Di nng lng i vi tinh thcng ha tr

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Vng ha tr: L vng c nng lng thp nht theo thang nng lng, l vngm in tblin kt mnh vi nguyn tv khng linh ng.

Vng dn: Vng c mc nng lng cao nht, l vng m in tslinh ng(nhcc in ttdo) v in tvng ny sl in tdn, c ngha l cht sckhnng dn in khi c in ttn ti trn vng dn. Tnh dn in tng khi mt

in ttrn vng dn tng.Vng cm (hay min cm): L vng nm gia vng ha trv vng dn, khng

c mc nng lng no v do in tkhng thtn ti trn vng cm.

i vi tinh th cng ha tr (chng hn tinh th kim cng), cc di nnglng ng vi MO lin kt v di phn lin kt (di dn in) nm cch bit nhau (bigi tr ). Vi cht bn dn hay cht cch in th di ha tr hon ton bo haelectron, trong khi di dn in hon ton cn trng (theo gin trn).

Khi electron chuyn t vng MO ln vng MO*, th trong di dn in michuyn ng tdo di tc dng ca in trng ngoi.

Khc vi kim loi, cc tinh thcng ho trdo c c min cm, nn sdchchuyn electron ln cc MO*i hi phi tiu tn mt nng lng nht nh l .

V vy, mt cht sl cht cch in, khi min cm qu rng kckhi c stng tc ca nng lng in, in t. Lc ny cc electron khng thchuyn ngln min dn.

Trong thc t, iu kin thng, mt cht c coi l cht cch in, khi rng ca min cm c gi tr vo khong 3eV. Vi cht bn dn th rng camin cm nhhn.

Bng 8. rng ca min cm ca mt snguyn tTinh th Kim cng Si Ge Sn (dng )

[eV] 6,00 1,10 0,70 0,08

Tbng trn ta thy, kim cng l cht cch in, cc tinh th trn l chtbn dn.

4.5. Tinh thphn t

4.5.1. Lin kt ha hc trong tinh thphn t

Trong tinh thphn t, mng li khng gian c cu to bi cc phn tnhCO2, I2, H2O, N2,... cng nhnguyn tca cc kh tr.

Hnh 31. M hnh tinh thphn tca it

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4.5.2. Cu trc ca tinh thphn t

Nhng tinh thca cc kh trl nhng tinh thphn tn gin nht vmtcu trc. V phn tca kh trl phn tn nguyn t, nn cu tca tinh thlnguyn thnh cu. Lc tng tc y chl lc khuch tn khng nh hng.

Nhng tinh thphn tthng gp nht l tinh thca cc hp cht hu c.

Do c stham gia ca lin kt cu ni hiro nn nc c cu trc tdin.Cu trc ny c xp ln ngha l c tkhi nh. V vy OoC, nc nhhnnc.

Hnh 32. Cu trc tdin cnc

Mi phn tnc c khnng to 4 mi lin kt hiro vi 4 phn tkhc nmchung quanh v hnh thnh cch sp xp kiu tdin trong nc .

Sbn ha cu trc ca nc c thxy ra khng nhng do c mt cc ionltrng ca n, m cn do a thm vo nhng phn tto c lin kt hiro vicc phn tnc. ng thi cu trc ca nc c lm bn, khi nc cn nm trng thi lng v khi trn ln n vi cht khc.

4.5.3. Tnh cht ca tinh thphn t.

Tinh thphn tc cng nh, v nng lng tng tc gia cc phn tcgi trnh(lin kt bi lc van de van - lc ny yu hn so vi lin kt ha hc), nnnhit nng chy ca chng thp.

Cc tinh thphn ttan tt, nhng sla chn cc dung mi phthuc vo bncht ca cc cht, m trc ht vo phn cc gia chng v khnng hnh thnhlin kt hiro.

Cc tinh th phn t dn, cng thp, chng khng c tnh dn in (trnhng cu trc kiu graft cha hthng chung lin kt pi khng nh ch).

4.6. Cht rn v nh hnh, tinh thlng v trng thi lng4.6.1. Cht rn v nh hnh

Cht rn v nh hnh l nhng cht rn m vcu trc vi m khng c sphnbmt cch tun hon u n cc cu tcbn trong ton khi cht rn.

V d: Thy tinh, cao su, nha,

Cc cht rn v nh hnh thng thng c sn xut khi mt cht lng nhtblm lnh rt nhanh, v thkhng c thi giancc mt li tinh ththngthng c thto thnh.

Cht rn v nh hnh c tnh ng hng, ngha l nhng tnh cht vt l nh:in tr, dn in,.. u ging nhau theo mi hng.

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Cht rn v nh hnh khng c nhit nng chy xc nh. Khi nhit tng,tnh linh ng ca cc ht tng theo v cht rn v nh hnh chuyn sang trng thilng. Sut trong qu trnh nng chy, nhit lun thay i.

Trong nhng iu kin khc nhau, khi chuyn t trng thi nng chy sangtrng thi rn, nhiu n cht nhSe, S, P, cng nhnhiu hp cht nh, (c bit l

cc oxit SiO2, GeO2, As2O3,) c thtn ti dng tinh thhay dng v nh hnh.Chng hn nhcao su, thy tinh.

Do nhiu hiu ng khc nhau, skt tinh c thbcn trv khi lm lnh dinhit kt tinh, cht nng chy chuyn thnh cht lng qu lnh.

i vi nhiu cht trong iu kin qu lnh, ti mt khong nhit qu lnh,ti mt khong nhit xc nh, nht tng nhanh dn n sngng hon ton cachuyn ng tnh tin v ta c trng thi thy tinh. Vmt cu trc, khi to thnh thytinh, cc tdin [SiO4]

4-trong pha lng khng chuyn vdng trt t, m tn ti trongcht rn mt cch khng trt t, hay v dnh hnh.

l mt cht rn v nh hnhng nht, c gc silictThy tinh (SiO2), thngc pha trn thm cc tp cht c tnh cht theo mun. Thy tinh thun SiO2(cn gi l thy tinh thch anh). C hai hp cht thng thng hay c bsung voct trong cng nghnu thy tinh nhm gim nhit nng chy ca n xung khong1.000 C. Mt trong s l s a(cacbonat natriNa2CO3), haybtt(tc cacbonatkaliK2CO3). Thy tinh c sdng rng ri trong xy ng, lm cha (chai, l,cc, chn, ly, tch, v.v) hay vt liu trang tr.

4.6.2. Tinh thlng

Tinh thlng l cc cht lng hu cc trt tcu trc. Tinh thlng chim vtr trung gian gia cht lng v cht rn. Do tng tc c bit, gia cc phn tcuto tinh thlng c sp xp theo trt tnht nh, thhin tnh dhng nhtinh th,nhng chng li c linh ng nhcht lng.

Mt s tinh th lng (trung gian gia tinh thv v nh hnh), ngay c thytinh cng thhin tnh dhng nhng dhng gin on chc cht kt tinh.

Mt shp cht hu cc thtn ti trng thi tinh thlng. Khi nng chy,cc cht ny trthnh trthnh mt cht lng c. Khi tip tc un nng, th ti mtnhit nht nh, cht lng ny trnn trong sut v ng thi cng trnn nghng vtnh chit quang.

mng li tinh th, cc phn tca cc hp cht trn nh hng song songvi nhau. Khi nng chy, chng c khnng chuyn ng tdo, tuy nhin khi vntn ti nhng gm hng triu phn tm trong vn cn snh hng song songca cc phn t. Stng tc gia nh sng v cc khu vc vi mt sphn bctrt tv gy nn hin tng chit quang kp.

Chuyn ng tnh tin tng cng vi s tng ca nhit v ti nhit nhtnh, trt ttrong cc phn tbph v. Ti nhit ny, hp cht trn chuyn ttrng thi tinh thlng sang trng thi ng hng bnh thng.

iu kin cn thit ca vic xut hin trng thi tinh thlng l phn tca hpcht phi c mt dng thch hp (mch di) v phi c mt momen lng cc vnh cu

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hay momen cm ng. Vi iu kin ny, cc phn tmi c khnng tng tc vicc phn tbn cnh v dn n snh hng song song ca chng.

4.6.3. Trng thi lng

a. Khi nim

Khi lm ngui cc cht trng thi kh, hay nn cc cht kh tht mnh, lc tngtc gia cc phn tbt u tri hn nng lng chuyn ng ca chng, v nhit xc nh (ring cho tng cht), cht kh chuyn qua trng thi lng.

Cht lng l mt trng thi vt chtkh phbin, m cc phn tcu to nn nc lin kt khng cht so vi lin kt rnv c hnh dng phthuc vo vt cha n.

b. Lin kt trong cht lng

Lc lin kt trong cht lng c quyt nh bi cu to hnh hc v cu toelectron ca nguyn thay phn ttrong cht lng. Ty theo slin kt ha hc giacc phn t, ngi ta phn bit cht lng c cc hay khng c cc )0( = .

Khi kim loi trng thi lng, lc lin kt gia cc nguyn t l lc lin ktkim loi. M bn cht ca lin kt kim loi l lin kt khng c hng, nn c thcho

php cc nguyn tlin kt thay i vtr ca mnh m khng cn phi bt t. V vykim loi in hnh phi c im nng chy thp v im si cao. Ngha l trng thilng ca kim loi phi ng vi mt khong nhit rng.

V d, Gali l cht lng nhit t32 22400C. Nhng a skim loi, cbit l cc nguyn td, th gia cc nguyn tngoi vic xut hin lin kt kim loicn xut hin lin kt nguyn t(lin kt c hng trong khng gian), dn n stngmnh nhit nng chy ca chng.

Vi mui chy lng, th lc lin kt gia cation v anion l tng tc tnh inging tinh thion.

Khi trng thi nng chy, thtch cht lng thng chthay i 10% so viban u. iu c ngha l khong cch gia cc cu tchbin thin khong viphn trm (do c sbay hi).

c. Cu trc ca cht lng

Kt qunghin cu cho thy cht lng tn ti nhng nhm phn tm trong cc phn tcng c phn b theo mt trt tno , c gi l trt tgn. Tuy

nhin cc nhm ny lin tc c hnh thnh ri tgii tn. trng thi lng, cc phn tdao ng chung quanh mt vtr cn bng tm

thi trong mt nhm ri chuyn ng tnh tin sang mt vtr cn bng khc. Nhit cng cao th thi gian ctr ca phn tmt nhm cng ngn. V vy, nhit cngcao trng thi lng cng gn vi trng thi kh.

d. Tnh cht ca cht lng

Sc cng b mt c nh ngha l lc cng trn mt n v chiu di ctngang bmt. Trong ho lng quc t, sc cng bmt c o bngNewtontrnmt(N.m-1). Hoc c thnh ngha sc cng bmt l cng chcthc hin khi lc

cng lm cho din tchbmt thay i mt n vo din tch.

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Sc cng bmt ca cht lng ph thuc vo nng lng tng tc gia ccphn t(hoc cc nguyn t) ca cht.

Khi un nng cht lng, lc tng tc gia cc tiu phn ca n yu i, v sccng bmt gim xung. nhit no , sc cng bmt bng khng, gi l nhitti hn.

Cht lng c khuynh hng lm gim sc cng bmt bng cch gim dintch b mt, l nguyn nhn lm cht lng d to thnh nhng git khi cu cng knh khc nhau v cc git dnhp li thnh git ln.

Thi gian di ch cht lng l cng tiu th vn chuyn cht lng theong ng phthuc vo nht cht lng.

nht l tnh cht cc lp cht lng cn li schuyn ng ca lp ny ivi lp kia, l thng si din cho ma st trongca dng chy.

. .F S

=

F l lc cn thit lm chuyn dch lp cht lng ny so vi lp cht lng kia.

S : l din tch tip xc gia hai lp cht lng.

: l hiu stc hai lp.

: l khong cch hai lp.

: L nht, phthuc vo bn cht ca cc cht, khi tng nhit nht cc chtlng u gim.

Thnguyn ca nht: khi lng/ di thi gian, trong hCGSE n

tng ng g/cm.s. n v ny gi l poaz (P) v bng lc ma st trn 1cm2, nunhng lp cch nhau 1cm c tc chuyn ng khc nhau 1cm/s.

nht ca cht lng khc nhau kh nhiu. Khi tng nhit , nht ca chtlng gim, iu ny c lin quan n sgim lc tng tc gia cc tiu phn. V d,gim ca nc khi un nng t0 n 900C gim 5 ln.

Thng thng nhit si ca cc cht lng tng khi phn tkhi ca chngtng, v lc ny lc tng tc tng do cng tnh ca lc khuch tn.

Stng phn cc ca cc phn tdn n stng lc nh hng v do cng dn n stng nhit si.

i vi cc hirocacbon c lin kt i, nhit si tng cng vi stng cahlin hp, v trong trng hp ny khnng phn cc ha tng v do lm tng lclin kt gia cc phn t.

4.7. Hp cht cao phn t(polime)

4.7.1. Cu trc v c im

Cc polime c hnh thnh khi cc phn t thng thng kt hp vi nhauthnh mch di, do cc lin kt ha hc c hnh thnh gia chng. Khi nu cc

phn tban u ging nhau (A), th to thnh phn tln polime ng thkiu: - A A A A A - (A l gc ca phn tban u).

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Cc Polime thng phn nhnh gm cc phn trt di, di ca chng vtqu dy ca chng hng chc nghn ln.

C 2 loi cu trc polime: dng vin v dng b.

Cu trc polime dng vin: khi to thnh t cc monome, chng dbnt ratheo ng ranh gii phn cch gia cc vin v dbph v. Nu cc vin xp cht

hn, khi ranh gii gia chng bxi mn, th vt liu polime trnn trong sut v bn.Nhvy vi cu trc dng vin, nht ca dung dch cht polime rt nh.

Vi cu trc dng b: cc mch phn t ln thp vi nhau, thu c nhngtp hp thng, l nhng b phn tln. iu ny xy ra l do cc phn tln ringrkhng thco trn li thnh vin.

4.7.2. Tnh cht v ng dng.

a. Tnh cht

Vt liu polime rt phbin trong thc t, do nhiu nguyn nhn:

- Sa dng vcc tnh cht ca vt liu polime: rn v mm, n hi, do, nh,...- Tng i dchto thnh sn phm.

- Tng i rv dkim nguyn liu (than, du m, kh).

- Bn i vi tc dng ha hc - bn vi sn mn.

C 3 loi bin dng tn ti vt liu polime:

- Bin dng n hi,

- Bin dng n tnh cao.

- Bin dng chy.Khi c tc ng bn ngoi ln polime th cu trc ca n c xy dng li dn

dn - c gi l shi phc. Sbin dng n hi c lin quan n sbin i gcha trgia cc nguyn ttrong mch polime. Sbin dng chy gy ra bi schuyndch cc phn tln i vi nhau, lc ny cc polime sthhin nhcht lng.

b. ng dng

* Sho tan polime

Polime a nc: polime c cu trc mch thng c thtan hoc trng mnh

trong nc. Thuc loi ny c cc nhm c cc cha cc nguyn t O v N trongthnh phn phn t, cc nguyn tny to lin kt vi hidro.

lm dung mi cho cc loi polime, ngi ta s dng cc hidrocacbon:benzen, xng, axeton, ru,...iu ny c gii thch do nhng phn tnhca dungmi i vo polime v gy nn qu trnh trng ln ca polime trong dung mi.

Mt spolime c nht cao v c tnh dnh cao, l do trong dung dch polimecha cc phn tln v tng tc mnh. Khnng kt dnh cng cao khi tng nng ca polime trong dung dch v khi hnhit . Dung dch polime thuc loi ny l hv sn.

* Nu chy polimePolime khi nu chy tn ti 2 dng: hp cht do nng v hp cht cng nng.

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18/20

Polime do nng khi un nng bmm ra v nng chy, cn khi lm lnh chngha cng. Thuc kiu ny c polietylen, polistirol, capron,...chng gm nhng phn tln hoc phn nhnh, cc phn tny khi un nng chng khng bkhu li thnhcu trc li.

Polime cng nng khi un nng skhng nng chy v khng ha tan, do xy

ra phn ng gia cc polime ca chng to thnh cu trc dng li. Thuc kiu nyc nha phenolfomanehit, nha ny l csca bakelit, cacbolit. Tchng ngi tachto cc sn phm cng v bn nh: thn my in thoi, vdng cin,...

* Sha do cc vt liu

iu kin tinh khit cc polime khng c tnh n hi cao, tuy nhin c thto polime cng c khnng bin dng n hi cao bng cch thm vo chng nhngcht thp phn tno y c khnng lm tng ng thi tnh do ca vt liu. Chtthp phn tnhthgi l cht do ha.

Cht do ha sdng c tnh c trng: nht cao, t bay hi.

Mc ch chyu cht thp phn tkhi a vo polime l hnhit thy tinhha ca polime, bin chng mm hn v mrng vng bin dng n tnh cao m polime c sdng.

Chng hn: nhit thng, polivinyclorua l polime rt cng, c nhit thu tinh ha +750C. Thm thm dibutylftalat c th h nhit thy tinh ha i1000C v thu c vt liu c tnh mm v tnh n hi khc nhau.

* Ssi bt ca polime

Cc cht do xp hp thnh mt nhm cht do c bit, l nhng vt liu

tng i mi. N c sdng chto cc toa lm lnh, cc thit blm lnh, ccphao tiu,...N c iu chbng cch cho nha tng hp vo bt c, bt ny rnli di dng tong cha cc lnh, hoc bng cch thi kh vo cht do clm mm.

Trong kthut xy dng, ngi ta sdng chyu cc cht do rtong. to chng, ngi ta p mt slp giy i dng tong. Sau tm ln bng nhngcht nha nhn to ri bt mt u hoc chai u bng cht do bn chc hn.

* n cc polime.

hgi thnh polime, ngi ta thm vo chng cht n: mhng, cao lanh,

mt ca,...cht n lm thay i tnh cht polime: lm gim ttrng, lm tng bn.* Cu tng ha cc polime.

Nhm mc ch l cnh cc phn tln vi nhau nhhnh thnh cc lin ktha hc gia chng v chuyn thnh cht do. Qu trnh ny tin hnh khng cn cht

phgia, nhqu trnh a ngng tgia nhng nhm chc tdo ca cc phn tlncn. Qu trnh nhthgi l sha cng.

V d: Slu ha cao su.- CH = CH - - CH - CH -

+S8 Sn Sn- CH = CH - - CH - CH -

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* Gii thiu mt shp cht cao phn t.

- Polietylen (PE): c dng lm cht do trong k thut in, bao b, dng dndng,...

- Higt density polietylen (HDPE): c iu chtnha PE c cho thm cht chngoxy ho, cht n nh v cht mu cn thit. c im quan trng l loi nha ny rtdo, bn ha cao.

- Polistyren: c dng lm vt liu cch in, sn xut mt sdng cquang hc,dng cvn phng,...

- Polivinylclorua (PVC): c dng lm vt liu cch in, ng nc, vi che ma,...

- Polivinylaxetat: c khnng kt dnh tt vo thy tinh, kim loi, g,... nn c dngchto sn v keo dn.

- Polimetylmetacrylat: c tnh chu nhit, chu va chm v bn c hc cao (chu

c 700 kg/cm2), nn c dng lm knh kh v.- Polibutadien: c dng lm cao su nhn to.

- Poliamit: c dng ko tdt vi may mc. c bit dng may o cu ha.

- Poliphenolfomandehit:

+ Nu dng xc tc H+, ly dphenol, to ra novolac: c dng to sn,vecni.

CH2

OH OH

CH2 n[ ]

OH

+ Khi dng xc tc OH-, ly dfomandehit, c poli zezol:

CH2

OH OH

CH2n[ ]

OH

CH2OH

CH2OH

CH2OH

HOCH2

- Poliurefomanehit: c dng lm keo dn, cht do, pha sn.

NH CO NH CH2 NH CO NH CH2 N CH2 NH CO NH

CO NH CH2OH

- Poli epoxit: dng lm keo dn,

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20/20

Cu hi v bi tp

1. Hy nu cu trc v tnh cht ca tinh th? ngha ca tbo sng? Cc mngli Brave?

2. Hy nu cu trc v tnh cht ca tinh thnguyn t. Cho v d. Gii thch v saokim cng, than ch, than hot tnh u c cu to bi slin kt ca cacbon, nhngkim cng li c cng ln nht?

3. Hy nu cu trc v tnh cht ca tinh thphn t? Cho v d.

4. Hy nu cu trc v tnh cht ca tinh thion? Cho v d. Khi nim vchsphitr. ngha ca n trong vic gii thch bn cht ca lin kt trong tinh th.

5. Hy nu cu trc v tnh cht ca tinh thkim loi? Cho v d.

6. ng dng m hnh di nng lng gii thch mt stnh cht vt l ca kim

loi.7. Phn tch cc kiu mng tinh thca kim loi so snh xc nh tnh cng v tnhdo ca kim loi. Gii thch ng dng ca n trong cng nghvt liu kim loi.

8. So snh skhc nhau gia cht rn v nh hnh v cht rn tinh th?

9. Khi nim tinh thlng v trng thi lng? ngha ca sc cng bmt v nht.

10. Hy nu mt sng dng thc tca hp cht cao phn t(polime)?

mang tinh the

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