Giáo trình vật lý đại cương phần nhiệt học vật lý phân tử ths nguyễn hoàng tuyến, ths nguyễn thị ngọc vân

Mot trong nhtfng yeu to trong yeu la doi ngu thay co, he thong cac giao trinh va trang thiet bi day hoc.Cung vdi cdc nganh cac cap trong toan quoc dang day nhanh tien do xay dang va cung

Nguyen Hoang Tuyen - Nguydn Thi Ngoc Van

Giao Trinh

Phan Nhiet Hoc & Vat Ly Phan TuT

LiCu hanh noi bo

Vlnh Long - 2009

TRUONG DAI HOC DAN LAP CtfU LONG

th L vi £ n I

Trircrng Dai hoc Dan lap Cufu Long muon khang dinh la trung tam dao tao nguon nhan lilc co trinh do cao cho khu vile dong bang song Cdu Long de phuc vu cho ebng cuoc cong nghiep hoa, hien dai hoa dat nifo’c thi phai nang cao chat hftfng dao tao toan dien Mot trong nhtfng yeu to trong yeu la doi ngu thay co, he thong cac giao trinh va trang thiet bi day hoc.Cung vdi cdc nganh cac cap trong toan quoc dang day nhanh tien do xay dang va cung co vi the trong xu the hoi nhap, triicrng Dai hoc Dan lap Cdu Long dan tiing bifdc hoan thien de difctag dau vcfi nhtfng thach thiic do, gop phan diia nen giao due dai hoc Viet Nam dufng vang, ngang tam khu vqc va the gidi.

Ke hoach xay dang ve mot Bo giao trinh sd dung cho cac giang vien lam tai lieu co ban de giang day, cho sinh vien nghien cdu tham khao hoc tap la nhu cau cap bach cua nha tradng

An pham nay la giao trinh Vat Ly Dai Caong - Phan Nhiet Hoc & Vat Ly Phan Td cua Khoa Khoa Hoc Co Ban, Tradng Dai hoc Dan lap Cdu Long, do ThS Nguyen Hoang Tuyen va ThS Nguydn Thi Ngoc Van bien scan

Lanh dao tradng Dai hoc Dan lap Cdu Long tran trong nhdng cong hien, dong gop cua Quy thay cd mbi giang cung nha cac thay cd can bd - giang vien co' hdu cua nha trabng

ThS Nguyen Cao Dat

t

trong nha trtfcfng.

Tran trong gidi thieu gido trinh nay den Quy thay co va

cac em sinh vien triTbng Dai hoc Dan lap Cdu Long.

Vinh Long, thang 09 nam 2009

Q HIEU TRLfdNG

NHIET HOC

Ccf hoc nghien ctfu nhtfng quy luat van dong don gian nhat cua vat chat, do la sif chuyen dong cua vat the trong khong gian Khi khao sdt van dong co hoc, ta chOa quan tam den nhtfng hien tiTo'ng xay ra ben trong vat, ta chifa xet den nhtfng qua trinh cd lien quan den cau tao vat chat cua vat Thqc te cd rat nhieu hien tifOng lien quan den cac qua trinh xay ra ben trong vat Vi du : vat cd the ndng chay hoac bdc hoi khi bi dun ndng, vat se ndng len khi chiu life ma sat,

Nhtfng hien tiTOng nay lien quan den mot dang chuyen dong dac biet cua vat chat, do la chuyen dong nhiet Viec nghien cdu chuyen dong nhiet la nhiem vu cua bo mon Nhiet hoc

Nhiet hoc Id ngdnh vat ly nghien cilu dang nhiet cua chuyen dong vat chdt vd nhUng quy luat cua chuyen dong do Tuy

nhien, nhiet hoc con nghien cdu ca nhtfng hien tifqng dien, tit

va nhieu hien tiTOng khac d cac vat Doi vdi nhilng hien tirqng nay, nd tien hanh nghien ctfu tren quan diem xet nhtfng dac diem cua dang chuyen dong nhiet

Trong lich suf, nhiet hoc da xuat hien dau tien nhu" la nganh nghien cdu sif chuyen hda tir nhiet ra edng co hoc (may hoi nude), nen con goi la nhiet dong life hoc Ve sau, cac dang khac cua nang lifOng (dien nang, hda nang, nang lifOng bdc xa, ) dan dan di/qc difa vao linh vifc nghien cdu cua nhiet dong life hoc, va bo mon nay cd the diXOc xem la khoa hoc ve nang IdOng

VAT LY PHAN TLf

<

<

Vat ly ph&n tic Id mot ngdnh vat ly nghien ciCu sU cdu thank

vd cdc tinh chtit cua vdt chtit diCa tren co sd quan diem dong

hoc phdn tic Theo quan diem nay, mot vat bat ky (cr moi trang

thai ran, long, khi) khong la mot moi trirdng vat chat lien tuc,

ma difoc cau tao tu" mot so" rat Idn cac hat rieng biet rat nho,

goi la phan tih Cac phan tuf cua moi chat deu chuyen dong hbn

loan khong ngiing, cifcfng do chuyen dong phu thuoc vao nhiet

do cua chat

Vat ly phan th co muc tieu la giai thlch cac tinh chat cua cac

vat cd the quan sat trite tiep tren thitc nghiem (ap suat, nhiet

do, ) nhit la ket qua tac dung tong hop cua tap the nhieu phan

tut Dong thdi nd sit dung phitOng phap thong ke, bang each

khong quan tarn den sit chuyen dong cua tifng phan tut rieng

biet ma chi quan tarn den cac gia tri trung binh dac trifng cho

chuyen dong cua vd so hat Tit do nd con cd ten goi la vat ly

thong ke

Cung nhit nhiet dong life hoc, ddi titqng cua vat ly thong ke

la nhitng quy luat cua dang chuyen dong nhiet cua vat chat

Vat ly thong ke chi khac nhiet dong lite hoc ve phitong phap

nghien cutu Trong khi nhiet dong life hoc khong ke den ban

chat phan tu" cua cac chat thi vat ly th d'ng ke lai xuat phat tit

ban chat nay, nd con su* dung rdng rai nhitng dit kien ve cau

tao phan tit va ap dung nhitng dinh luat ve xac suat Vat ly

thong ke cho phep giai thich y nghia vat ly cua cac dai litqng

nhiet dong, tim ditqc gia tri tuyet dd'i cua nhitng dai litqng nay

ma nhiet dong lite hoc chi cho nhitng gia tri titong ddi

Chutcfng 1.

THUYET DONG HOC PHAN TLf VE CHAT KHI

- KHf LY TtfdNG

I THUYET DONG HOC PHAN Ttf VE VAT CHAT

Vat ly phan til nghien ctfu cac hien tifcfng nhiet tren cP scr ly thuyet ve cau true hat cua vat chat, life tuPng tac gitfa cac hat

va chuyen dong cua chung Ly thuyet nay duPc goi la thuyet dong hoc phan tuf

1 Thuyet dpng hoc phan td

Thuyet dong hoc phan tuf gom 3 luan diem co ban sau :

1/ Vat chat difOc cau tao th vo so” cac phan td nhd be goi la phan tcf Phan td la phan to be nhd nhat co the phan chia ra dope td vat chat ma vdn gid nguyen moi tinh chat hda hoc cua vat chat ay

Neu xet sau hOn, ta thay phan td con co the phan chia thanh cac nguyen td, nguyen td lai dupe cau tao td cdc hat: electron, proton va neutron (trong co cau hat nhan) Tuy nhien,

d day chi xet cau true vat chat den mdc dp phan td ma thdi.2/ Phan td cau thanh vat chat chuyen dong hdn loan khdng ngdng, goi la chuyen dong nhiet

3/ Trong qua trinh chuyen dong nhiet, cac phan td tuong tac nhau do va cham, chung hut hoac day nhau

Tuy trang thai vat chat la khi, long hay ran ma tUOng tac phan td cd the manh hay yeu

2 Dien giai

Cac so lieu sau day la bang chtfng xac minh sq dung dan cua cac luan diem cua thuyet dong hoc phan td :

- So' luWng phan tuT trong mot khoi vat chat rat Idn Vi du, trong 1 kmol khf bat ky co No = 6,023 x 1026 phan td (so Avogadro).

- Rich thiTdc cac phan td rat be Neu coi phan td nhb mot qua cau thi difcfng kfnh cua no vao khoang 1O~10 m

- Cac phan td khong nSm sat nhau Do do, tong the tich rieng cua cac phan td nhd hcfn the tich cua toan bo vat Doi vdi chat long, tong the tich rieng cua cac phan td chiem khoang the tich toan bo Doi vdi chat khi, tong the tich rieng cua cac phan

td chiem khoang 1/1000 the tich toan bo, cho nen kich thutfc phan td nhd thua hang chuc lan khoang each gitfa cac phan td

- Moi phan td la mot he hat mang dien bi phan cite, vi vay chung tiTcfng tac life tinh dien veri nhau Thifc nghiem cho thay tuy theo khoang each r gitfa cac phan td, life tiTcfng tac phan td

co the la life day hoac hut : khi r<3xl0-10m cac phan td day nhau, khi r > 3 x IO-10 m cac phan td hut nhau ; life hut giam nhanh khi r tang, d nhufng khoang each r > 15 x IO-10 m, life tifefng tac phan td rat nhd co the bd qua Nhir vay, d dieu kien ap suat va nhiet do thirdng, ta cd the bd qua life hut gida cac phan

td khi

3 Vai hi£n tiTorng dien hinh phan anh dac diem can tao phan til cua vat chat

a) Chuyen dong Brown

Nhin cac hat phan hoa (kich thifdc vao ccf pm) trong nifdc qua kfnh hien vi, ta thay chung chuyen dong vdi quy dao la cac difdng gap khuc bat ky Chuyen dong nay goi la chuyen dong Brown

Gidi thick :

Chuyen dong Brown cd dude la do chuyen dong hdn loan khong ngdng cua cac phan td ntfdc That vay, trong khi cac

phan tii nifo’c chuyen dong, chung luon va cham vao cac hat phan hoa Vi cac hat phan hoa cd kich thifdc qua nhd nen cac

va cham cua cdc phan th niftfc len chung khong khd l^n nhau

Do ngau nhien, so' va cham theo mot hifdng nao do nhieu hon, ket qua la hat phan hoa se chuyen dong theo hildng do Sau khi hat phan hoa di diTOc mot doan, no lai bi cac phan th nude day

ve mot hu’o’ng khac Vi vay, quy dao cua cac hat phan hoa la cac dufrng zic-zac

Ta co the ket luan : chuyen dong hon loan khong ngiTng cua cac hat phan hoa trong nifdc phan anh chuyen dong nhiet cua cac phan th nud’e

b) Hien tityng khuech tan

Nho mot giot thudc tim vao mot chen nude yen lang Thoat dau, ta thay vung mau tim rat hep va cd ranh gid’i ro ret dd'i vdi vung nude xung quanh De cang lau vung cd mau cang nhat, vung mau tim lan ra xung quanh va khong cd ranh gidi rd ret nhif trudc do

Vay, d day do chuyen dong nhiet, cac phan td thudc tim va cac phan tuC mrdc da hoa lan vao nhau Do la hien tirqng khuech tan phan tu*

Vdi chat khi va chat rdn cung xay ra hien tdOng khuech tan phan td Vi du : bang phien khuech tan vao khong khi, dong va thiec khi tiep xue lau cung khuech tan vao nhau

II THUYET DONG HOC PHAN Thf VE CHAT KHI - KHI LY TLfdNG

1 Mau khi ly tudrng

Thuyet dong hoc phan tuf ve chat khi la sir van dung thuyet dong hoc phan tut vao viec nghien cdu chat khi Thuyet nay nghien ciiu chat khi bang edeh diTa ra mot “mo hinh chat khi” nham dd khao sat, goi la “mdu khi ly tirdng”, trong do cd ap

dung cac dinh luat cua ctf hoc co dien va van dung phtfcfng phap tho’ng ke.

Mau khi ly ttfdng diTOc mo ta bang bon luan diem sau day :1/ Khi ly tifdng ditoc cau thanh bdi mot so rat Idn cac phan

td The tfch m6i phan td rat nhd so vdi the tich khi chiem.2/ Chuyen dong cua cac phan td la hon loan khong ngdng (chuyen dong nhiet) va tuan theo cac dinh luat cua ccf hoc Newton

3/ Cac phan td chi tifcfng tac nhau khi va cham, con luc khong va cham, ItTc tifOng tac co the bo qua

4/ Sir va cham gida cac phan td khi vdi nhau hay gida cac phan td l<hi va thanh binh la tuyet doi dan hoi, nghia la trddc

va sau va cham tong dong nang cua cac phan td khong doi

2 Dien giai

- Trong dieu kien binh thdbng, trong 1mm3 khong khi (hay cac chat khi khac) cung chda khoang 3 x 1016 phan td Day la mot so' rat 1cm cac phan td

- 6 ap suat thdbng (latm), khoang each trung binh gida cac phan td khi vao khoang 3 x 10-9 m, con ddbng kinh phan td khi vao khoang 2 x IO-10 m, nghia la nhd hern 1/10 khoang each gida chung Do do, cd the xem phan td khi la chat diem trong cac khao sat ccr hoc

- Khi khong cd ngoai Ide tac dung len cac phan td thi chung ddde phan bo deu trong toan bo the tich khi chiem

- Chuyen dong cua cdc phan td ngoai luc va cham la thing deu Cac va cham cd tac dung lam doi phdcrng va do Idn cua van tdc phan td

- Vi cac phan td chuyen dong nhiet, nen trong khoi khi khong cd hddng du tien, tdc la moi hdd'ng doi vdi chuyen dong

phan tuf la dong kha nang Do Idn van toe co the lay tif gia tri rat be den gia tri rat Idn, nhifng khong the la Idn vo han He qua nay la dac trifng quan trong cua chuyen dong nhiet.

NhUng han ch$ cua mdu khi ly tiCdng :

Mdu nay chi dung trong chiTng mifc ma co hoc cd dien con cd the ap dung dittfc

Cac luan diem ve khi ly tifdng chi ap dung cho khi thqc trong nhdng dieu kien ap suat, the tich va nhiet do nhat dinh, khong khac cac dieu kien thifdng

3 Phtfotag trinh cd ban cua thuyet dpng hoc phan tii khi

ly tu’dng

a) Ap suat chat khi

Khi dung trong binh tac dung len thanh binh mot ap suat Theo quan diem vi mo, ap suat cd gia tri bling life nen theo phuong vudng gdc len mot dun vi dien tich cua thanh binh.Goi AF la life nen cua khoi khi theo phUctag vudng gdc len dien tich AS cua thanh binh va gay nen ap suat P Ta cd

p=^

AS

Ta se tinh P theo quan diem vi mo va thuyet dong hoc phan

td bang each dung phiiOng phap thong ke Xet he true toa do Oxyz cd true Ox vudng gdc vdi dien tich AS tren thanh cua binh chda khi Xem cac phan td chi chuyen dong theo ba phUOng Ox, Oy va Oz vdi hai chieu dUcfng va am cua cac true Goi mat do phan td khi trong binh la n Trong n phan td nay

cd : njL, n2, phan td chuyen dong theo Ox vdi van tdc lan liMt la vx, v2, Suy ra so' phan td gay diicfc ap suat tren AS

la : lan luqt dd'i vdi cac phan td cd vx (loai 1), v2(loai 2),

0

thanh binhz

x

Xet rieng cac phan tuf loai 1 : trong khoang thfri gian dt, cac phan tur loai nay dich chuyen mot doan = Vidt Co bao nhieu phan tcf loai 1 dap vao dien tich AS trong khoang thdi gian dt ?

Xet mot hinh try day AS, chieu cao lx = Vj^dt Cac phan td nam trong hinh tru nay neu chuyen dong theo Ox ve phia AS thi sau thdi gian dt co the va cham vao AS

Hinh tru co the tich AV = ^AS, so" phan td trong hinh tru

n x AV = n x IjAS

Trong n x AV phan td, co ni x AV phan td cd van toe vj va

AV phan td loai 1 dap len AS va gay ap suat rieng cua chung

Ve mSt co hoc, m6i phan td loai 1 trutfc khi va cham co dong liiOng mv! va sau va cham co dong litong -mv-t (m : khoi ItiOng phan td, va cham la tuyet do'i dan hoi) Do do do bien thien dong liiOng cua mot phan td loai nay trong khoang thdi gian dt (trudc va sau va cham) la :

-mvj - mvj = -2mv1

Fx gay ap suat Px len AS :

Tifc/ng tif, ap suat theo phufcfng Oy va Oz cung diTtfc tmh :

i=l

= m InjVj + n2V2 + • • ■ + nnv:

-2mv1dKi =

SM);

i=l

i la van toe cdc phan tCr loai i theo cac phifcfng

Px = Fx = m AS

Ox, Oy, Oz

Vi cac phan td chuyen dong hdn loan, cac phitong la dong deu, khong cd phtfefng uti tien nen :

(1)Vay :

Wtt chinh la dong nang trung binh trong chuyen dong tinh tien cua cac phan td

nGoi : Wtt = 2

i=l

= mEni (c?) i=l

BjWjn

n 3P = m^nj (

i=ltrong do Ci la van toe phan td

P=-E^ 3 A' ni mefi=lk

o n iKniWt)

^Nhan xet :

• P ty le vdi n va Wtt, dieu nay ta dd dang nghiem thay

• P bieu thi tinh chat chung cua ca khoi khi, P ddqc goi la dai Idqng vi mo

• Wtt bieu thi chuyen dong cua tdng phan td, Wtt goi la dai lirqng vi mb

v?+uf+w?)

Phan ndng h/ang truyen til vat nong sang vat lanh got Id nhiet liiong.

Vat nong co dong nang tinh tien trung binh cua phan tuf Idn hern dong nang tinh tien trung binh cua phan td vat lanh Phan dong nang cua cac phan td cua vat nong hefn truyen cho cac phan td cua vat lanh hefn thong qua sir va cham trong qua trinh chuyen dong nhiet chinh la nhiet liTOng truyen

b) Dcfn vi do dp sudt

- Trong he SI : P do bang N / m2, dcfn vi nay con goi la Pascal

- Cac dcfn vi khac cua ap suat :

• milimet thuy ngan : mmHg, con goi la Torr

ImmHg la ap suat gay nen bd’i trong liiOng cot thuy ngan cao 1 mm

1 mmHg = 133,322 N/m2

• atmotphe vat ly : atm

latm la ap suat gay bdi trong luPng cot thuy ngan cao

760 mm

1 atm = 760mmHg = 1,013 x 105 N / m2

(3)Ket qua nay cho thay cac phan khf chuyen dong cang nhanh thi dong nang tinh tien trung binh Wtt cang 16n, nhiet

do 9 cua khi cang cao va ap suat P cua khf cang cao

Vay, nhiet do Id dai liMng dac tritng cho tinh chdt vi mo cua

vat, phdn dnh mdc do nhanh cham cua chuyen dong hon loan cua cac phdn td cdu thdnh vat Hay noi each khac, nhiet do la

so” do cifbng do chuyen dong hbn loan cua cac phan td cau tao nen vat, cung la so do dong nang trung binh cua chuyen dong tinh tien cua cac phan td trong vat

Vd’i quan niem tren, ta phai tinh nhiet do 0 bang don vi nang ItiPng (joule hoac erg, erg = 10-7J) Tuy nhien dieu nay rat khd khan, la vi :

• viec do trifc tiep Wtt cua phan td rat phde tap

• don vi nang liipng du nhd nhn erg , nhifng vein rat Idn neu dung de do nhiet do 0 Vf du nifdc da dang tan cd nhiet

do 0 chi vao bac 10~14erg

2 Nhi^t dp

Neu vat A nong hon vat B, ta thufrng noi nhiet do vat A cao ho'n nhiet do vat B Khi do, dong nang tinh tien trung binh cua cac phan td trong vat A Idn hon dong nang tinh tien trung binh cua cac phan td trong vat B

Nhit vay, co the dung dong nang tinh tien trung binh cua phan td trong vat lam thiidc do nhiet do cua vat De defn gian, ngifcfi ta quy udc nhiet do 0 cua vat diipc xac dinh bdi :

9

0 = ^WttoPhuOng trinh co ban (1) cd the viet :

P = n0

Cdc thang nhiet do thong dung :

Celsius (°C), Reaumur (°R), Fahrenheit (°F), Kelvin (K)

0 ap suat khi quyen binh thtfbng (760mmHg), nhiet do cua:

nhiet do cao nhatvao cd 100 trieu do Itftag

• nifdc da dang tan : 0°C = 0°R = 32° F = 273K

• hoi nude dang sdi : 100° C = 80° R = 212° F = 373K

Wtt=|kT,

• 6 nhiet do T = 0K, thi Wtt = 0, nghia la cac phan th ngifng chuyen dong tinh tien, nhung chung van con duy tri cac dang chuyen dong khac nhif sii dao dong OK gpi la do khong tuyet doi, thang nhiet do Kelvin con goi la thang nhiet do tuyet doi

• Nhiet do thap nhat dat dope hien nay xap xi 1,3 x 10" K,

vu nd bom nguyen

Viet lai phtfcfng trinh co’ ban :

Phiictag trinh (8) co du 3 thong sb P, V, T, nen diftfc goi la

phitcnig trinh trang thdi cua khi ly titdng.

N

p=vkT

• Trong nhiet dong life hoc, ngtfbi ta hay dung nhiet do tuyet doi

IV PHUONG TRINH TRANG THAI KHI LY TUdNG

Mot khdi khi ton tai trong trang thai can bang neu cdc dai ItiOng vi mb cua no khbng doi Nhtfng dai ItfOng vi mb xac dinh trang thai cua khdi Idii goi la cac thong so trang thai

Cac thong so trang thai cua khi ly tirb’ng gom co :

• The tich V (dbo'c xem la khoang khbng gian chuyen dong tu" do cua cac phan tu" khi, do chinh la the tich binh chda)

• Ap suat P

• Nhiet do T

Cac thong so nay khbng phai hoan toan doc lap nhau, ma co nhtfng mdi quan he nao do ddi vdi nhau Phi/ong trinh neu mdi lien he gitfa ba thong so P, V, T cua mot khdi lifqng m khi cho triib’c goi la phitong trinh trang thai

PhiTctag trinh trang thai cd dang tong quat : P = f(V, T)

Do do, neu biet dang cu the cua phiiOng trinh nay thi td hai thong so cho triTcfc ta co the tinh duPc thong so con lai, nghia

la co the xac dinh diTOc trang thai cua khdi khi

Suy ra :

(9)Vay:

Goi m la khoi liftfng cua khoi khi (tinh bang kg)

pt la khoi liltfng cua 1 kmol khi dang xet (tinh bang

so phan til co trong 1 kmol

(so-— = sb kmol cua khoi khi

M-"NT XT

N = —No h

Tir do, cong thdc (8) co the viet: PV = —NgkT

• l,38xl0"23Dat: R = Nok = 6,023 x 1026

R = 8,31 x 103(J/kmol.K), R goi la hang so khi ly tiring.

Neu xet 1 kmol khi : m = p., ta dutfc : PV = RT

Trong cac cong thufc (8), (9), P tinh bang , V tinh bang m3 , T tinh bang K

V CAC DINH LUAT THUG NGHIEM VE CHAT KHI

Vdi mot khoi khi xac dinh (m = const), gitf cd dinh mot trong ba thong sb trang thai (hoac T, hoac P, hoac V) thi th phtfcmg trinh Clapeyron — Mendeleev, ta tim diftfc moi quan he gitfa hai thong sb kia Cac ket qua suy bang ly thuyet nay phii hop vdi cac dinh luat ve chat khi von da tim done bang thifc nghiem thuan tuy trutfc khi ra ddi thuyet dong hoc phan til ve chat khi

_kg_) kmol 7

(ID

2 Dinh luat Gay Lussac

Xet mot khoi khi co khoi litong xac dinh (m = const), neu giu' ap suat khong doi (P = const), tif phirong trinh Clapeyron

— Mendeleev ta suy ra :

1 Dinh luat Boyle - Mariotte

Xet mot khoi khi cd khoi liitfng xac dinh (m = const), neu giur nhiet do khong doi (T = const), tit phifctag trinh Clapeyron

- Mendeleev ta suy ra :

» v

V

— = const T

Vay, voi mot khoi litgng khi xdc dinh, neu gid nhiet do khong doi khi thay doi trang thdi khi thi tich so cua dp sudt vdi the tich ludn Id hang so.

Qua trinh bien doi trang thai khi ma gid nhiet do khong doi goi la qua trinh dang nhiet

Chu y : dinh luat nay chi dung doi vdi cac chat khi d nhiet

do phdng va ap suat gan bdng ap suat khi quyen (1 atm) Neu

ap suat tang len qua 100 at thi se cd sai lech dang ke Nguyen nhan la do trong ly thuyet ta khong ke den tdOng tac gitfa cac phan td, ma d ap suat cao tiTOng tac nay khong the bo qua

P a

3 Dinh luat Charles

Xet mot khoi khl co khoi liTOng xac dinh (m = const), neu

gift the tfch khong doi (V = const), tit phiicfng trinh (9), ta suy

ra :

Vay, vai mot khoi litimg khl xac dinh, neu gid dp sudt khong doi khi thay doi trang thdi khl thi the tich vd nhiet do tuyet doi cua nd ty le vai nhau.

Qua trinh bien doi trang thai khl ma gitf ap suat khong doi goi la qua trinh ding ap

V a

P

— = const T

Vay, vui mot khoi lifting khi xac dinh, neu gid the tich khong doi khi thay doi trang thdi khi thi dp sudt vd nhiet do tuyet doi cua nd ty le vai nhau.

Qua trinh bien doi trang thai khl ma giCt the tich khong doi goi la qua trinh dang tich

P'b

P =

Cac dinh luat Gay Lussac va Charles cung chi gan dung nhif dinh luat Boyle - Mariotte

4 Dinh luat Dalton

Xet mot hdn hop gom n loai khf khac nhau, khong hoa hop vol nhau, cung chda trong mot binh the tfch V Goi N]^, N2,

Nn la so phan td cua cdc loai khl thd 1, thtf 2, thb n; N la tong so phan tuf khf trong binh

Vay, dp suat cua hdn hap khi bdng tong cac dp sudt rieng

phan cua cac khi thanh ph&n trong hdn hap.

Nhan xet :

Cac khi thanh phan gay ra ap suat mot each doc lap vdi nhau, nghia la trong tac dung gay ra ap suat cua loai khi nay khong ke den sir ton tai cua cac loai khf khac Sd di nhu" vay la

vi ddi vdi khf ly tOcrng, cac phan td ton tai doc lap ma khong tifong tac vdi cac phan td khac

£ Ket luan :

Sit phu hap khd tot giUa ly thuyet vd cac quy luat thUc nghiem chdt khi d dieu kien binh thuang chiing minh rdng thuydt dong hoc ph&n td la dung ddn Nhdng thieu sot trong

m&u khi ly tttdng se dilac bo sung vd pliUcmg trinh trang thdi se diloc hieu chink moi phan dnh ditoc ddc tinh cua chat khi trong thitc te.

Ghi chu:

Tif phiTcfng trinh Clapeyron - Mendeleev ta co the suy ra kho'i krcrng rieng p cua khi ly ttfdng (the la khdi lifPng ufng vdi mot defn vi the tlch)

4 Tlnh the tlch cua 10 g oxy d ap suat 750 mmHg va nhiet do 20° C

5 Mot binh co dung tlch 121 chtfa day nito d ap suat

8, lxlO6N/m2 va nhiet dp 17° C Hoi khdi lirpng nitP chtfa trong binh la bao nhieu ?

6 Mot khi cau co the tlch 300m3 Ngifbi ta bom vao khi cau nay khi hydro d nhiet do 20°C dtfdi dp suat 750mmHg Hoi sau bao lau thi bom xong ? Neu moi giay bom dope 2,5 g khi hydro

_ m _ pP

P - V ” RT

BAI TAP CHtfONG 1

1 Co 10g oxy d ap suat Sat, sau khi ho ndng ding ap no chiem the tlch 101 Tim nhiet do sau khi ho ndng Coi oxy la khi ly tudng

2 Trong mot binh the tlch 51 chila 1g hydro d nhiet dp 27° C Tlnh ap suat cua khdi khi nay

3 Tlnh nhiet dp cua 2 g khi nito chiem the tlch 820 cm3 d ap suat 2 at

7 Mot cai bom moi lan bom daoc 41 khong khl d ap suat 1 at

va o' nhiet do 17° C vao mot binh co the tlch 1,5 m3 Biet r^ng khong khi trong binh nong len tdi 45°C va co ap suat 2at Hoi phai bom bao nhieu lan ?

8 Mot binh chtfa mot chat khi nen d nhiet do 27° C va ap suat

40at Tim ap suat cua khi khi da co mot nila khoi loong khi thoat ra khoi binh va nhiet do ha xuohg tdi 12° C

9 Co 10 kg khi dong trong mot binh, ap suat 107 N/m2 Ngifbi

ta lay d binh ra mot lifOng khi cho tdi khi ap suat cua khi con lai trong binh bang 2,5 x 106 N / m2 Coi nhiet do cua khoi khi khong doi Tim lifOng khi da lay ra

10 Nung nong mot binh difng khi hydro nen co the tich 101 cr nhiet do 7°C va ap suat 50at Vi binh hb nen cd mot Itfcfng khi hydro thoat ra ngoai Ltfo’ng hydro con lai trong binh co nhiet do 17°C con ap suat van nhif cu Tinh khoi Icrcfrig khi hydro thoat ra ngoai

11 Mot hon hop khi gdm co 2,8 kg nitcf va 3,2 kg oxy b nhiet

do 17° C va ap suat 4 x 105 N / m2 Tim the tich cua hon hop

12 Mot binh the tich 3 dm3, chila 4xl0-6kg khi heli,

7 x 10-5 kg khi nito va 5 x 1021 phan tuf hydro, nhiet do cua khi phan boz deu va bang 27°C Tinh :

a Cac ap suat rieng phan cua cac thanh phan khi

b Ap suat cua hdn hop khi

13 Co 10 g oxy b ap suat 3 at va nhiet do 10° C Sau khi nung nong dang ap no chiem the tich 101 Tinh :

a The tich khoi khi trade khi nung

b Nhiet do khoi khf sau khi nung

Khoi lifo’ng rieng cua khi trifdc va sau khi nung

14 Trong binh chtfa 14 g niter va 9 g hydro cr nhiet do 10° C

va dp suat 106 N/ m2 Tim :

a Khoi krong 1 kmol hon hop

b Dung tich cua binh chila

15 The tich cua khong khi trong phong la 100 m3 Tinh khoi lifOng khong khi thoat ra khoi phong do khi nhiet do tif 10° C tang len 25°C , neu ap suat khf quyen bang 770 mmHg

16 Co hai binh chda hai thtf khi khac nhau thong vo’i nhau bang mot ohg thuy tinh co khoa The tich cua binh thd nhat la

21, cua binh thil hai la 31 Luc dau ta dong khoa, ap suat o’ hai binh lan loot la lat va Sat Sau do mb khoa nhe nhang

de hai binh thong nhau sao cho nhiet do van khong doi Tinh

ap suat cua h6n hop khi khi thong nhau

Chtfcfng 2

NGUYEN LY I NHIET DONG LUC HOC

Nguyen ly I nhiet dong life hoc la mot tien de, khong the chufng minh bang ly thuyet, no ditOc rut ra tif kinh nghiem trife tiep cua con ngifdi Nguyen ly nay gan lien vdi sir bao toan va chuyen ho a nang litong 6 nhiTng he vi mo co lien quan den nhCng hien tiTOng nhiet

I NHIET NANG CUA KHI LY TUdNG

1 Nhiet nang

Nhiet nang cua mot vat (con goi la nang htong chuyen dong nhiet) co gid tri bang tong dong nang cua tdt cd moi phdn tit tham gia chuyen dong nhiet cdu thdnh vat tiy.

Xet mot he co N phan td Goi W la dong nang trung binh cua cac phan tuf Theo dinh nghia tren, nhiet nang cua he bang

E = NW

Muon xac dinh nhiet nang E ta can biet dong nang trung binh W cua cac phan td thuoc he Dai lirqng W cd lien quan den khai niem so bac tit do cua phan tuf

2 So' bac tuf do

So bac tit do cua mot vat Id so toa do doc lap can thiet de xac dinh vi tri vd cdu hinh cua vat ay trong khong gian.

Ta se xac dinh so bac tif do cua cac loai phan td khi ly tirdng Sif phan loai khi ly tifdng dira tren so nguyen td hop thanh phan td cua khi

a) Khi dofn nguyen tut : mdi phan td chi cd mot nguyen td,

nhtr cac loai khi tref (He, Ar, Ne, ) Phan td loai nay chuyen

dong nhiT mot chat diem, nen xac dinh vi tri cua no b&ng ba toa do (x,y, z).

Do do, so bac tif do cua no la : i= 3

b) Khi litdng nguyen tit : moi phan tuf cd hai nguyen tuf, vi

du cac khi O2, H2, N2, CO, Cac phan td loai nay vda chuyen dong tinh tien vita chuyen dong quay

• Doi vdi chuyen dong tinh tien can ba toa do (x,y,z) de xac dinh khoi tarn cua phan th

• Ddi vdi chuyen dong quay, phan td loai nay chi co hai bac tu" do, vi no khong quay quanh true xuyen tarn hai nguyen

td d nhiet do thirdng

Do do, so bac tif do cua no la : i = 5(= 3 + 2)

c) Khi da nguyen tit: moi phan td co nhieu nguyen td (td 3

trd len), nhd cac khi H2O, CO2, CH4, NH3, Moi phan td loai nay ddtfc xem la mot vat rdn, vi no co nhieu hern hai chat diem (xem nguyen td la chat diem) va each nhau nhdng khoang each khong doi Phan td da nguyen td co ba toa do (x,y,z) xac dinh chuyen dong tinh tien cua khoi tam va ba toa do xac dinh chuyen dong quay

Do do, so bac td do cua no la : i= 6(= 3 + 3)

Vay, so bac td do cua phan td khi ly tdd'ng la :

3 doi vdi phan td khi do’n nguyen td

i= 5 doi vdi phan td khi Iddng nguyen td

6 doi vol phan td khi da nguyen td

d Chii y : d day ta chi gidi han xet cac phan td co lien ket ran chac (khoang each gida cac nguyen td trong mot phan td la khong doi) Trong trddng hop ngddc lai, xdc dinh chuyen dong phan td rat phde tap, so” bac td do cua no 16n hem

W = i —kT2

• Cong thiic nhiet n&ng cua khoi khl N phan tCf:

E = N.i —kT = — —RT

2 p 2trong do : m la khoi lifcrng khf, p la khoi litong 1 kmol khi ay

Do la noi dung dinh luat Boltzmann

Tif do, ta di den cac ket qua sau :

• Trong chuyen dong tinh tien, moi phan td deu co ba bac tq

do, vi vay dong n&ng tinh tien trung binh cua phan td la :

ma con co nghia doi vdi moi dang chuyen dong (tinh tien, quay, ), tdc la khong mot dang chuyen dong nao la itu tien hon

Td quan diem do, ngdbi ta dan den mot luan diem sau day :Dong nang trung binh cua phan td dng vdi moi bac td do deu bang vj-kT, khong phan biet chuyen dong tinh tien hay chuyen dong quay

Hay noi each khac :

Dong nang trung binh cua ph&n tii duuc phdn bo deu theo so bac tit do, dng vol mdi bac tu do dong nang trung binh la 77kT.

• Nhiet nang cua 1 kmol khi :

Vay doi vdi khi ly tifcfng :

H 2

Eo =iRT

0 2

II NQI NANG CUA KHI ly tU(3 ng

Noi nang cua mot vat boo gom cdc dang nang lugng ben

trong vat, no chi phu thuoc vdo trang thdi ben trong vat, nghia

la khong ke dong nang trong chuyen dong loan bo cua vat vd the nang cua vat trong trUdng ngodi.

Noi nang U cua he bao gom :

• Nhiet nang E cua he

• The nang tiTcfng tac gitfa cac phan tuf Et trong he

• Nang kfcmg noi phan td Ep,trong do co dong nang va the nang ttfctag tac gitfa cac electron va hat nhan nguyen tuf,

U = E + Et+EDKhi he thay doi trang thai, cac dang nang liTcfng tren bien thien cac lu’Ong dU , dE , dEt, dEp Ta cd :

dU = dE + dEt + dEDTrong cac bien doi trang thai cua he doi vdi nhiet dong life hoc thi nhiet do va dp suat khong qua cao va trang thai ben trong phan tuf van khong thay doi Tuf do nang luUng noi phan tuf la khong doi, tufe dEp = 0 Khi do :

dU = dE + dEtDoi vdi khi ly tufdng, ngufefi ta lai bo qua life taefng tac gitfa cac phan tuf khi, nghia la Et = 0 , nen dEt = 0

dU = dE = d|—^RT

trong do dT la do bien thien nhiet do cua he trong qua trinh bien doi vo cung be cua trang thai.

* Chu thick :

Lfng vdi mbi trang thai cua he, chi co mot gia tri cua noi nSng ma thbi Ta noi : noi ndng Id ham dan gid cua trang thai

Vay dU la vi phan toan phan

III CONG VA NHIET

Xet bieu thdc :

dU = — -RdT.

p 2

Ta thay rang neu nhiet do cua he thay doi thi noi nang cua

he cung thay doi theo, khi ay trang thai cua he thay doi, dong thdi he thifc hien mot qua trinh

Co the lam thay doi nhiet do va noi nang cua he bang hai each :

1 Bang cong co hoc : nen khi dot ngot, nhiet do khi tang ; dan khi dot ngot, nhiet do khi giam

2 Bang each truyen nhiet lupng cho he

Phan tich ta thay :

- Cong la hinh thufe truyen nang ItTOng gitta cac vat vi mo gan lien vdi sif chuyen dong cd hifdng cua vat xet ve toan bo

- Nhiet la hinh thifc truyen nang liTOng xay ra trifc tiep gitta cac phan td cau tao nen vat vdi nhau, khi va cham trong qua trinh chuyen dong nhiet

Cong va nhiet deu do ciing don vi cua nang lopng (joule), nhung chung khdng phai la nhtfng dang nang loqng ma chi la nhtfng phan nang lifqng da difqc trao doi gitta cac vat tiTOng tac.Doi vdi 1 kmol khi ly tirdng : dU0 = -^RdT

Cong va nhiet phu thuoc trifc tiep vao qua trinh bien doi trang thai, chung chi ton tai trong qua trinh Hay noi cdch khdc : cong va nhiet Id ham cua qua trinh.

Nay dA, dQ khong la vi phan toan phan.

Ngilcri ta thufrng ky hieu : 5A,8Q Nhimg tCr day ve sau, ta se dung ky hieu dA, dQ cho thuan tien

IV TRANG THAI CAN BANG - QUA TRINH CAN BANG

bang

Trong co hoc, trang thai can bang cua mot vat la trang thai

ma vat do ddng yen - doi vdi he quy chieu dang xet Trong nhiet dong life hoc, khai niem trang thai can bang diTOc hieu rong hon:

Mot he goi la ton tai trong mot trang thai edn bdng khi moi thong so cua he duqc hodn toan xdc dinh va neu khong co tdc dung ben ngodi thi he se ton tai mdi mdi trong trang thai do.

NhO vay, he d trang thai can bang khi ma trong he khong

co xay ra cac qua trinh truyen, cac phan ufng hoa hoc, cac bien doi pha, Tuy nhien, cac phan td cau thanh he cung van chuyen dong nhiet khong ngbng

Xet he d trang thai (1) chuyen sang trang thai (2) thong qua mot chuoi cac trang thai trung gian lien tiep (I), (II), (III), Ta noi he trai qua mot qua trinh Ro rang la moi trang thai trung gian ay deu la khong can bang, vi cac thong so' trang thai cua

he tai cac trang thai nay deu dang bien doi Tuy nhien, co nhiing qua trinh didn bien du cham, sao cho :

• Tai tifng thdi diem cdc thong so trang thdi co gid tri xac dinh

• Gid tri cua cac thong so thay doi it trong khoang thefi gian du be dt, trong dt nay, he diTOc xem la can bang

2 Cong h£ nhan trong qua trinh can biing

Ta tmh cong de nen mot khoi khi trong xilanh ditoc day kin bang pittong co dien tich day S

P2

Pl

as

Qua trinh nhif the goi la qua trinh chudn cdn bting, nghia la

gan nhif can bang

Qua trinh cdn bdng la mot qua trinh bien dot he gom mot chudi lien tiep cdc trqng thdi cdn bdng.

NhiT da thay d tren, trong thi/c te khong co qua trinh hoan toan can bang Trong van de khao sat cac qua trinh bien doi

he, ta thifdng gia thiet he bien doi du cham de qua trinh xay ra

la chuan can bang, khi do viec xem he thiTc hien qua trinh can bang la gan dung nham thuan tien cho viec tinh toan Tren he toa do PV, mbi trang thai can bang ditoc bieu dibn bang mot diem co toa do (V, P) chfnh la gia tri cua the tich va ap suat cua he Tif do qua trinh can bang diftfc bieu dibn bang mot dirbng lien tuc tren he true nay

Pt

la F' va F' = -F.

A' = -A =

dQ = mcdT

Do do :

1 l.atm = 24,2cal = 101,3 Jleal = 4,186 J; 1J = 0,24cal

a) Nhiet dung rieng

Nhiet dung rieng cua mot chat Id mot dai liiqng vat ly co gid tri bdng nhiet liiqng edn truyen cho mot dan vi khdi liiqng chdt

do de lam tang nhiet do ten 1 do.

Xet mot he cd khoi lifOng m, nhan nhiet Idtfng dQ thi nhiet

do tang len mot lifOng dT Theo dinh nghia, nhiet dung rieng c cua he diTtfc tfnh:

dQ

c mdT

rv2

Co the chilng minh rSng cac ket qua tren day cung dung doi vdi cac qua trinh can bang tong quat, trong do stf bien doi the tich la bat ky

Ghi chu : neu ap suat tinh bang atm va the tich tinh bang

lit, cong diroc tinh bang lit.atm Muon chuyen sang dem vi joule hay calo, can nhd :

Do doi

const), ta cd nhiet dung

b) Nhiet dung rieng phan tic

Nhiet dung rieng phan tit cua mot chdt co gid tri bang nhiet htang cdn truy&n cho 1 kmol chdt dy de lam tang nhiet do len 1

do, ky hieu C.

trong do la khoi liTOng 1 kmol (tmh bang kg) cua chat ay

Trong do, c tinh bang ; C tinh bang R

V NGUYEN LY I NHIET DONG LUC HOC

1 Dinh luat bao toan va chuyen hoa nang hTorng

Van dong la thuoc tinh cua vat chat Vat chat co vo so' cac hinh thtfc van dong khac nhau Tuy nhien, mdc do van dong cua vat chat cd the liTOng hda chung nhat bang khai niem nang lifo’ng:

Nang htong chinh Id so do mite do udn dong cua vat chdt trong moi bien ddi cua no tit dang nay sang dang khac.

So' do d day difo'c hieu theo nghia pho quat, tdc la dai lao'ng

dac trifng cho ca mat dinh tinh lan dinh litong cua sir van dong Noi dung cua hai mat nay dirqc the hien trong dinh luat bao toan va chuyen hda nang liftfng :

Nang litong khong tit sinh ra ma cung khong tit mdt di, no chi chuyen hoa tit dang nay sang dang khac hay tit he nay sang

he kia.

dQ = —CdT

• Trong qua trinh dang tich (V = const), ta cd nhiet dung rieng phdn td dang tich, ky hieu Cv

• Trong qua trinh dang dp (P

rieng phdn tit dang dp, ky hieu Cp

Trong do, c tinh bang ; C tinh bang

Ve mat dinh litong, dinh luat nay Idling dinh ring trong he

co lap, ddi vdi moi qua trinh bat ky, nang Ihtfng luon luon diTOc bao toan, nang laqng chi cd the chuyen tir dang nay sang dang khac theo nhtfng ty le dinh lifdng xac dinh

Ve mat dinh tinh, dinh luat nay khang dinh sif bao toan cua van dong vat chat trong kha n&ng vd tan chuyen hda qua lai td dang nay sang dang khac

Tom lai, dinh luat bao toan va chuyen hda nang lifcfng phan anh sit bat diet cua van dong vat chat

2 Nguyen ly I nhi^t dpng Itfc hoc

Khi xet tren quan diem nhiet dong life hoc, he cd the trao doi n&ng liTdng vdi ben ngoai thong qua sit trao ddi edng va nhiet He nhif vay goi la he nhiet dong Do edng va nhiet la tiTOng dirong nhau, nen neu he chi trao doi edng va nhiet vdi ngoai vat thi cd the phat bieu dinh luat bao toan va chuyen hda nang lirqng nhif sau:

Do bien thien nang litgng cua he trong mot qua trinh bien doi trang thdi bdng tong edng va nhiet ma he nhqn dilgc trong qua trinh do.

Neu goi Wj, W2 la nang lirqng cua he d trang thai dau va trang thai cuoi trong mot qua trinh bien ddi trang thai, A, Q

la edng va nhiet ma he nhan dirqc trong qua trinh nay thi ta cd

AW = W2 - Wx = A + QNeu ca he ddng yen (tren toan bd) va khdng d&t trong mot trirdng life nao thi nang lirqng cua he chinh la ndi nang cua nd :

W = U

Khi do, edng thtfc tren dirqc viet nhiT sau :

AU = U2 - Uj = A + Q

3) Neu he la co lap, nghia la he khong trao doi cong va nhiet vdi ngoai vat, khi do :

A = Q = 0^AU = 0->U = constVay noi nang cua mot he co lap daoc bao toan

trong do : Ux, U2 lan liTOt la noi nang cua he d cac trang thai dau va trang thai cudi

Cong thufc nay la noi dung cua nguyen ly I nhiet dong life hoc, phat bieu nhif sau : Do bien thi&n noi nang cua he trong mot qua trinh bien doi trang thai bting tong cd ng va nhiet ma

he nhqn diloc trong qua trinh do.

Doi vdi mot qua trinh bien doi vo cimg be, cong thu’e nay dirqc viet dutfi dang vi phan : dU = dA + dQ

3 Hq qua cua nguyen ly I nhiqt dpng Itfc hoc

Th cong thde cua nguyen ly I, ta dan ra cac he qua sau :1) Neu A > 0,Q > 0 thi AU > 0 Dieu nay co nghia la neu he thu’e sir nhan cong va nhan nhiet thi noi nang cua he tang Do tang noi nang cua he dung bhng tong cong va nhiet he nhan difqc tir ben ngoai

Neu A < 0, Q < 0 thi AU < 0, nghia la neu he thifc sir sinh cong va toa nhiet thi noi nang cua he giam Do giam noi nang cua he dung bang tong edng sinh ra va nhiet toa ra cua he.2) Neu ngoai nhiet va cong, con co cac tac dung khac cua ngoai vat tham gia vao viec lam bien doi trang thai cua he (nhir dien triTcmg, th triThng, ), thi co the quy moi tac dung do

ve tong edng thefng dhong ^2 Aj Do do :

i

AU = U2 -Ux = Aj

<Tl)

(AT = T2Mat khac :

Suy ra :

• Vo’i khi dtfn nguyen tu" :

• Vo'i khi lircfng nguyen th :

• Vdi khi da nguyen th :

-R 2

4 Dpng cof vinh ctfu loai I

Trong dong co nhiet, he nhiet dong thOc hien mot so rat Idn

cac chu trinh Chu trinh (con goi la qua trinh kin) la mot qua

trinh bien doi he ma trang thdi dau va trang thai cuoi trung

nhau Trong mot chu trinh, ta luon co :

AU = 0 —> A = —Q

Q = —CVAT

Neu Q > 0 thi A < 0 Dieu nay co nghia la he muon sinh

cong thi phai nhan nhiet Khong the cd dong co nhiet nao sinh

cong ma khong nhan nhiet, the khong tieu thu nang Mong

Loai dong co nhiet gia tuhng chi sinh cong ma khong nhan

nhiet, goi la dong co vinh chu loai I Th ket qua nay, nguyen ly

I con cd the phat bieu dildi dang sau :

“KJidng the thuc hien ditqc dong ca vinh cdu loai I”.

VI tfNG DUNG CUA NGUYEN LY I VAO CAC QUA TRINH

CAN BANG DAC BIET

1 Qua trinh dang tich

2 Qua trinh dang ap

• Vdi khi do'n nguyen td :

• Vdi khi lirdng nguyen td :

• Vdi khi da nguyen tuT:

dutfc gpi la he so Poisson.

q = HIraT + — RAT = — - + 1 RAT