Cov lus nug piv txwv ntawm Txoj Cai Dub

15 Piv txwv ntawm Cov Lus Nug Txog Lub Ntsiab Cai ntawm Dub

1. Muab dej khov uas hnyav 0,2 kg sib xyaw nrog tshuaj yej sov uas hnyav 0,2 kg. Qhov kub ntawm dej khov = - 10^oC, qhov kub ntawm tshuaj yej sov = 40^oC. Qhov kub tshwj xeeb ntawm dej khov = 2100 J/kg C^o, qhov kub tshwj xeeb ntawm dej = 4200 J/kg C^o, qhov kub ntawm kev sib xyaw ntawm dej = 334.000 J/kg. Yog tias dej khov thiab tshuaj yej kub raug sib xyaw ua ke hauv ib lub kaw lus kaw, txiav txim siab qhov kub kawg ntawm qhov sib tov.

Kev Sib Tham
Nws yog paub :
Qhov hnyav ntawm dej khov (m es) = 0,2 kg
Qhov hnyav ntawm dej tshuaj yej sov (m tshuaj yej) = 0,2 kg
Cov cua sov tshwj xeeb ntawm dej (c dej) = 4180 J/kg C^o
Qhov kub tshwj xeeb ntawm dej khov (c es) = 2100 J/kg C^o
Kub ntawm kev sib xyaw ntawm dej (L)_f dej) = 334.000 J/kg
Qhov kub ntawm dej khov (T es) = -10^oC
Kub ntawm dej tshuaj yej sov (T tshuaj yej) = 40^oC
Nug : qhov kub kawg ntawm qhov sib tov (T sib tov)?
Jawb :
Kauj ruam thawj zaug, kwv yees qhov xwm txheej kawg.
Qhov kub uas yuav tsum tau tso tawm los ntawm dej kom txo qhov kub ntawm 0,2 kg ntawm cov tshuaj yej sov los ntawm 40^oC txog 0^oC:
Cov cua sov uas nqus los ntawm 0,2 kg ntawm dej khov ua rau nws qhov kub nce ntxiv los ntawm -10^oC txog 0^oC:
Kub nqus kom yaj 0,2 kg dej khov (kub xav tau kom hloov tag nrho cov dej khov mus ua dej):
Raws li cov kev xam suav saum toj no, cov txiaj ntsig hauv qab no tau txais:
Q tso tawm = 33,444 kJ
Q tau txais = 4,2 kJ
Q yaj = 66,8 kJ

Thaum tshuaj yej kub tso tawm 33,44 kJ ntawm qhov kub, qhov kub ntawm tshuaj yej kub hloov pauv ntawm 40oC mus rau 0oC. Ib feem ntawm cov cua sov tso tawm (kwv yees li 4,2 kJ) yog siv los ua kom qhov kub ntawm cov dej khov nce ntawm -10 ° C mus rau 0 ° C. ^oC txog 0^oC. 33,44 kJ – 4,2 kJ = 29,24 kJ. Yuav kom yaj tag nrho cov dej khov mus ua dej, yuav tsum muaj 66,8 kJ ntawm cua sov. Qhov cua sov seem yog 29,24 kJ.

Nws tuaj yeem xaus lus tias qhov cua sov uas tso tawm los ntawm tshuaj yej sov tsuas yog siv los ua kom qhov kub ntawm cov dej khov nce ntxiv los ntawm -10 ^oC txog 0^oC thiab yaj qee cov dej khov. Qee cov dej khov tau hloov mus ua dej, qee cov tsis tau. Thaum lub sijhawm hloov pauv ntawm cov khoom khov mus rau cov kua, qhov kub tsis hloov. Yog li ntawd, qhov kub kawg ntawm qhov sib tov yog 0^oC.

2. Qhov hnyav ntawm cov tshuaj yej kub = 0,4 kg, qhov hnyav ntawm dej khov = 0,2 kg, qhov kub ntawm cov dej khov nab kuab = -10^oC, kub tshuaj yej kub = 90^oC. Yog tias ob qho tib si sib xyaw ua ke, qhov kub kawg ntawm qhov sib tov yog dab tsi?
Kev Sib Tham
Kauj ruam thawj zaug: kwv yees qhov xwm txheej kawg
Cov cua sov uas yuav tsum tau tso tawm los ntawm dej kom txo qhov kub ntawm 0,4 kg ntawm cov dej tshuaj yej kub los ntawm 90^oC txog 0^oC:
Lub cua sov uas tau txais los ntawm 0,2 kg ntawm dej khov kom tsa nws qhov kub ntawm -10^oC txog 0^oC:
Qhov kub uas xav tau los yaj 0,2 kg dej khov (qhov kub uas xav tau los hloov tag nrho cov dej khov mus ua dej):
Raws li cov kev xam suav saum toj no, cov txiaj ntsig hauv qab no tau txais:
Q tso tawm = 150,48 kJ
Q tau txais = 4,2 kJ
Q yaj = 66,8 kJ
Thaum tshuaj yej kub tso tawm 150,48 kJ ntawm qhov kub, qhov kub ntawm tshuaj yej kub hloov ntawm 90oC mus rau 0oC. Ib feem ntawm cov cua sov tso tawm (4,2 J) yog siv los tsa qhov kub ntawm cov dej khov ntawm -10 oC mus rau 0oC. 150,48 kJ - 4,8 kJ = 146,28 kJ. Qhov kub seem = 146,28 kJ.
Qhov kub uas xav tau los yaj tag nrho cov dej khov rau hauv dej tsuas yog 66,8 kJ. 146,28 kJ – 66,8 kJ = 79,48 kJ. Tshuaj yej kub tsis tas yuav tso nws cov cua sov tag nrho kom txog thaum nws qhov kub poob rau 0.^oC. Xaus lus, qhov kub kawg ntawm qhov sib tov yuav tsum ntau dua 0^oC.

Kauj ruam thib ob: txiav txim siab qhov kub kawg (T)
Qhov kub uas xav tau los ua kom qhov kub ntawm dej khov nce ntawm -10^oC txog 0^oC yog 4200 J.
Lub cua sov uas xav tau los yaj tag nrho cov dej khov rau hauv dej (latent heat) = 66.800 J
Qhov kub uas xav tau los ua kom dej kub (dej los ntawm kev yaj tag nrho cov dej khov) nce ntawm 0^oC txog T^oC = (qhov hnyav ntawm dej khov) (qhov kub tshwj xeeb ntawm dej) (T - 0) = (0,2) (4180) (T) = 836 T
Lub cua sov uas tso tawm los ntawm tshuaj yej sov kom txo nws qhov kub ntawm 90oC mus rau T = (qhov ceev ntawm dej) (90-T) = (0,4) (4180) (90 - T) = 1672 (90-T) = 150.480 - 1672 T

 

3. 60 grams dej ntawm qhov kub ntawm 90^oC (qhov kub tshwj xeeb ntawm dej = 1 cal.g^-1.^oC^-1) sib xyaw nrog 40 grams dej zoo sib xws ntawm qhov kub ntawm 25^oC. Yog tias tsis muaj lwm yam cuam tshuam rau cov txheej txheem no, ces qhov kub kawg ntawm qhov sib tov yog ...

A. 15,4 ^oC
B. 23,0 ^oC
C. 46,0 ^oC
D. 64,0 ^oC
E. 77,0 ^oC

Kev Sib Tham
Nws yog paub :
Qhov hnyav ntawm dej 1 (m₁) = 60 grams
Kub ntawm dej 1 (T)₁= 90 TZS^oC
Qhov hnyav ntawm dej 2 (m₂) = 40 grams
Kub ntawm dej 2 (T)₂= 25 TZS^oC
Cov cua sov tshwj xeeb dej (c) = 1 cal.g^-1.^oC^-1
Nug : suhu kev sib xyaw zaum kawg
Jawb :
Cov cua sov uas dej kub siab tso tawm (Q tso tawm) = cov cua sov uas dej kub qis nqus tau (Q nqus tau)
m₁ c (ΔT) = m₂ c (ΔT)
(60)(1)(90 – T) = (40)(1)(T – 25)
(60)(90 – T) = (40)(T – 25)
5400 – 60T = 40T – 1000
5400 + 1000 = 40T + 60T
6400 = 100T
T = 6400/100
TXL = 64^oC
Cov lus teb yog D.

4. Ib daim txhuas muaj qhov hnyav li 500 grams thiab muaj qhov kub ntawm 30 ^oC muab tso rau hauv ib lub thawv uas muaj dej nrog qhov hnyav ntawm 200 grams thiab qhov kub ntawm 90 ^oC. Yog tias qhov kub tshwj xeeb ntawm txhuas paub tias yog 0,22 cal/g C^o thiab qhov kub tshwj xeeb ntawm dej yog 1 cal/g C^o, ces qhov kub kawg ntawm dej thiab txhuas yog...
A. 20,3 ^oC
B. 42,2 ^oC
C. 68,7 ^oC
D. 80,5 ^oC
E. 100 ^oC
Kev Sib Tham:
Lub chav ntawm qhov hnyav, grams (g) tsis tas yuav hloov mus rau kilograms (kg) vim tias qhov kub tshwj xeeb ntawm txhuas thiab qhov kub tshwj xeeb ntawm dej tau qhia hauv cal / g C^o.
Nws yog paub :
m txhuas = 500 grams
c txhuas = 0,22 cal/gC^o
T txhuas = 30 ^oC
m dej = 200 grams
c dej = 1 cal/gC^o
T dej = 90 ^oC
Nug :
Qhov kub kawg (T) ntawm dej thiab txhuas?
Jawb :

Cov mis kub Q = (m)(c)(delta T)

Q dej = = (200 grams)(1 cal/gC)^o)(90 ^oC-T)
Q txhuas = (500 grams)(0,22 cal/gC^o)(T– 30 ^oC)

Cov mis yooj yim ntawm dub : Q _tawm = Q _{nqus tau}

Dej muaj qhov kub pib siab dua (90 ^oC) yog li ntawd dej tso cua sov, txhuas muaj qhov kub qis dua (30 ^oC) kom txhuas nqus tau cua sov. Qhov kub kawg ntawm qhov sib tov ntawm dej thiab txhuas yuav tsum qis dua qhov kub pib ntawm dej thiab siab dua qhov kub pib ntawm txhuas.
(200 grams)(1 cal/gC^o)(90 ^oC – T) = (500 grams)(0,22 cal/g C^o)(T– 30 ^oC)
(200)(1)(90-T) = (500)(0,22)(T-30)
(200)(90-T) = (110)(T-30)
18000 – 200 T = 110 T – 3300
18000 + 3300 = 110 T + 200 T
21300 = 310 T
TXL = 68,7 ^oC
Qhov kub kawg ntawm kev sib xyaw ua ke ntawm dej thiab txhuas yog 68,7 ^oC.
Cov lus teb yog C.

5. Ib daim hlau uas hnyav 300 grams ntawm qhov kub ntawm 80 ^oNcuav 200 grams ntawm cov dej npau rau hauv 40 feeb. ^oC. Qhov kub tshwj xeeb ntawm dej = 1 cal/g C^oYog tias qhov kub kawg ntawm cov hlau thiab dej sib xyaw yog 50^o C thiab lub thawv tsis nqus cua sov, ces qhov cua sov tshwj xeeb ntawm cov hlau yog ...
A. 0,15 cal/g C^o
B. 0,22 cal/g C^o
C. 1,50 cal/g C^o
D. 4,8 cal/g C^o
E. 7,2 cal/g C^o
Kev Sib Tham:
Nws yog paub :
m hlau = 300 grams
T hlau = 80 ^oC
m dej = 200 grams
T dej = 40 ^oC
c dej = 1 cal/g C^o
T qhov sib tov kawg ntawm hlau thiab dej = 50 ^oC
Nug :
c hlau?
Jawb :
Q hlau = (m)(c)(delta T) = (300 grams)(c hlau)(80^oC - 50^oC) = (300 grams)(c hlau)(30 C^o)
Q dej = (m)(c)(delta T) = (200 grams)(1 cal/g C^o)(60^oC - 50^oC) = (200 grams)(1 cal/g C^o)(10 C^o)

Cov mis yooj yim ntawm dub : Q _tawm = Q _{nqus tau}

Cov hlau muaj qhov kub pib siab dua (80 ^oC) yog li ntawd cov hlau tso cua sov, cov dej muaj qhov kub qis dua (40 ^oC) kom cov dej nqus tau cua sov.
(300 grams)(c hlau)(30 C^o) = (200 grams)(1 cal/g C^o)(10 C^o)
(300)(c)(30) = (200)(1)(10)
9000 c = 2000
c = 2000 / 9000
c = 0,22 cal/g C^o
Cov cua sov tshwj xeeb ntawm cov hlau yog 0,22 cal/g C^o.
Cov lus teb yog B.

6. Ob lub pob zoo sib xws muaj tib qhov kub ntawm 40 ^oC, ob lub pob muaj qhov hnyav ntawm 10 grams thiab 40 grams raws li. Ob lub pob raug muab tso rau hauv cov kua dej, yog li qhov kub ntawm ob lub pob nce mus txog 60^oC. Yog tias qhov kub tshwj xeeb ntawm lub pob yog 2 cal/gr C^o thiab 1 calorie = 4,2 Joules, ces qhov sib txawv ntawm cua sov uas txhua lub pob nqus tau yog ...
A. 5,04 x 10³ Joule
B. 7,50 x 10³ Joule
C. 10,6 x 10³ Joule
D. 40 x 10³ Joule
E. 42 x 10³ Joule
Kev Sib Tham:
Nws yog paub :
m₁ = 10 grams
m₂ = 40 grams
T₁ = T ua₂ = 40 ^oC
T _xaus = 60 ^oC
c pob = 2 cal/gr C^o
Nug :
Qhov txawv ntawm qhov kub uas txhua lub pob nqus tau yog dab tsi?
Jawb :
Qhov kub ntawm ob lub pob nce ntxiv vim tias ob lub pob yuav tsum nqus cua sov.
Q₁ = (10 gr)(2 cal/gr C^o)(60^oC–40^oC) = (10 gr)(2 cal/gr C^o)(20 C^o) = 400 cal = (400)(4,2 J) = 1680 Joules
Q₂ = (40 gr)(2 cal/gr C^o)(60^oC–40^oC) = (40 gr)(2 cal/gr C^o)(20 C^o) = 1600 cal = (1600)(4,2 J) = 6720 Joules
Qhov sib txawv ntawm cua sov uas txhua lub pob nqus tau:
6720 J - 1680 J = 5040 J = 5,04 x 10³ J
Cov lus teb yog lawm yog A.

7. Dej uas hnyav 200 grams ntawm qhov kub 30°C sib xyaw nrog dej npau uas hnyav 100 grams thiab qhov kub 90°C. (Qhov kub tshwj xeeb ntawm dej = 1 cal.gram^-1° C^-1). Qhov kub ntawm cov dej sib xyaw thaum lub sijhawm thermal equilibrium yog….

A. 10°C

B. 30°C

C. 50°C

Kub: 75°C

Kub ntawm 150°C

Kev Sib Tham

Nws yog paub :

Qhov hnyav ntawm dej 1 (m₁) = 200 grams

Kub ntawm dej 1 (T)₁= 30 TZS^oC

Qhov hnyav ntawm dej 2 (m₂) = 100 grams

Kub ntawm dej 2 (T)₂= 90 TZS^oC

Qhov kub tshwj xeeb ntawm dej (c) = 1 cal.gram^-1° C^-1

Nug : qhov kub kawg ntawm qhov sib tov

Jawb :

Cov cua sov uas dej kub siab tso tawm (Q tso tawm) = cov cua sov uas dej kub qis nqus tau (Q nqus tau)

Cov lus teb yog C.

8. Atxog li 60 grams ntawm qhov kub ntawm 90^oC (qhov kub tshwj xeeb ntawm dej = 1 cal.g^-1.^oC^-1) sib xyaw nrog 40 grams dej zoo sib xws ntawm qhov kub ntawm 25^oC. Yog tias tsis muaj lwm yam cuam tshuam rau cov txheej txheem no, ces qhov kub kawg ntawm qhov sib tov yog ...

A. 15,4 ^oC

B. 23,0 ^oC

C. 46,0 ^oC

D. 64,0 ^oC

E. 77,0 ^oC

Kev Sib Tham

Nws yog paub :

Qhov hnyav ntawm dej 1 (m₁) = 60 grams

Kub ntawm dej 1 (T)₁= 90 TZS^oC

Qhov hnyav ntawm dej 2 (m₂) = 40 grams

Kub ntawm dej 2 (T)₂= 25 TZS^oC

Qhov kub tshwj xeeb ntawm dej (c) = 1 cal.g^-1.^oC^-1

Nug : qhov kub kawg ntawm qhov sib tov

Jawb :

Cov cua sov uas dej kub siab tso tawm (Q tso tawm) = cov cua sov uas dej kub qis nqus tau (Q nqus tau)

Cov lus teb yog D.

9. Dej khov uas muaj qhov hnyav ntawm M grams ntawm qhov kub ntawm 0^oC, muab tso rau hauv dej uas hnyav 340 grams ntawm qhov kub ntawm 20^oC muab tso rau hauv ib lub thawv tshwj xeeb. Xav tias lub thawv tsis nqus/tso cua sov tawm. Yog tias L_es = 80 calorie g^-1, c_{huab cua} = 1 calorie g^{-1 o}C^-1, tag nrho cov dej khov yaj thiab thermal equilibrium raug ncav cuag ntawm qhov kub ntawm 5^oC, ces qhov hnyav ntawm dej khov (M) yog ...

A. 60 grams

B. 68 grams

C. 75 grams

D. 80 grams

E. 170 grams

Kev Sib Tham

Nws yog paub :

Qhov hnyav ntawm dej (m) = 340 grams

Kub ntawm dej khov (T_es= 0 TZS^oC

Kub ntawm dej (T)_{huab cua}= 20 TZS^oC

Qhov kub thiab txias sib npaug (T) = 5^oC

Kub ntawm kev sib xyaw ntawm dej khov (L)_es) = 80 calorie g^-1

Qhov kub tshwj xeeb ntawm dej (c_{huab cua}) = 1 calorie g^{-1 o}C^-1

Nug Qhov hnyav ntawm dej khov (M)

Jawb :

Txoj Cai Dub hais tias nyob rau hauv ib lub kaw lus kaw uas raug cais tawm, qhov kub uas tso tawm los ntawm ib yam khoom kub siab yog tib yam li qhov kub uas nqus los ntawm ib yam khoom kub qis.

Cov cua sov uas dej tso tawm (Q tso tawm) = cov dej khov nqus cua sov (Q nqus)

Cov lus teb yog lawm yog A.

Catatan :

Yog hais tias dej khov muaj qhov kub ntawm 0^o ces cov dej tseem nyob hauv daim ntawv khov kho. Yog tias nws tau hais tias qhov kub ntawm dej yog 0^oC ces dej yog kua. Sib txawv ntawm kev siv cov lus dej khov thiab dej. Vim tias dej tseem nyob hauv daim ntawv khov lossis khov, qhov cua sov uas nqus ua ntej yog siv los yaj tag nrho cov dej khov rau hauv dej, yog li ntawm sab xis ntawm kab zauv saum toj no, ib daim ntawv qhia tau ntxiv los xam qhov cua sov kom yaj cov dej khov (m_es L_es). Tom qab tag nrho cov dej khov tau yaj mus ua dej, cua sov ntxiv yog siv los tsa qhov kub ntawm cov dej khov los ntawm 0^oC dhau los ua 5^oC.

10. Tooj liab hlau ntawm qhov kub ntawm 100^oC muab tso rau hauv dej nrog qhov hnyav ntawm 128 grams thiab qhov kub ntawm 30 ^oC. Qhov kub tshwj xeeb ntawm dej 1 cal.g^{-1 Nws}C^-1 thiab qhov kub tshwj xeeb ntawm tooj liab yog 0,1 cal.g^{-1 Nws}C^-1Yog tias qhov sib npaug ntawm qhov kub thiab txias tshwm sim ntawm qhov kub ntawm 36 ^oC, ces qhov hnyav ntawm cov hlau yog ....

A. 140 grams

B. 120 grams

C. 100 grams

D. 80 grams

E. 75 grams

Kev Sib Tham

Nws paub tias:

Kub ntawm tooj liab (T₁= 100 TZS ^oC

Cov cua sov tshwj xeeb ntawm tooj liab (c₁) = 0,1 cal.g^{-1 Nws}C^-1

Qhov hnyav ntawm dej (m₂) = 128 grams

Kub ntawm dej (T)₂= 30 TZS ^oC

Qhov kub tshwj xeeb ntawm dej (c₂) = 1 cal.g^{-1 Nws}C^-1

Qhov kub thiab txias sib npaug (T) = 36 ^oC

Nug: Qhov hnyav ntawm tooj liab (m₁)

Lus teb:

Txoj cai ntawm Black hais tias qhov kub uas ib yam khoom kub siab tso tawm = qhov kub uas ib yam khoom kub qis tau txais.

Cov lus teb yog B.

11. Peb kilograms ntawm cov pas nrig dub nrog lub cua sov tshwj xeeb ntawm 1400 J.kg^-1C^-1 kub 80^oC raug muab tso rau hauv 10 kg dej nrog qhov kub tshwj xeeb ntawm 4200 J.kg.^-1C^-1Tom qab qhov sib npaug ntawm thermal tshwm sim, qhov kub kawg ntawm qhov sib tov yog 20^oC. Qhov kub ntawm dej pib yog….

A. 20 ^oC

B. 18 ^oC

C. 14 ^oC

D. 12 ^oC

E. 10 ^oC

Kev Sib Tham

Nws paub tias:

Qhov hnyav ntawm cov hlau lead (m₁) = 3 kg

Qhov kub tshwj xeeb ntawm tin (c₁) = 1400 J.kg^-1C^-1

Kub ntawm cov hlau nplaum (T)₁= 80 TZS ^oC

Qhov hnyav ntawm dej (m₂) = 10 kg

Qhov kub tshwj xeeb ntawm dej (c₂) = 4200 J.kg^-1C^-1

Qhov kub thiab txias sib npaug (T) = 20 ^oC

Nug: Qhov kub ntawm dej pib (T)₂)

Lus teb:

Cov lus teb yog C.

12. Ib lub npib 50 gram raug cua sov rau qhov kub ntawm 85^oC, ces muab tso rau hauv ib lub thawv uas muaj 50 grams dej ntawm qhov kub ntawm 29,8^oC (qhov kub tshwj xeeb ntawm dej = 1 cal.g^-1.^oC^-1). Yog tias qhov kub kawg ntawm lub kaw lus yog 37^oC thiab xav tias tsis muaj kev hloov pauv ntawm cua sov los ntawm lub nkoj, ces qhov cua sov tshwj xeeb ntawm cov hlau yog ...

A. 0,12 cal.g^-1.^oC^-1

B. 0,30 cal.g^-1.^oC^-1

C. 1,50 cal.g^-1.^oC^-1

D. 4,8 cal.g^-1.^oC^-1

E. 7,2 cal.g^-1.^oC^-1

Kev Sib Tham

Nws paub tias:

Qhov hnyav ntawm npib (m) = 50 grams

Kub pib ntawm lub npib (T)₁= 85 TZS^oC

Qhov hnyav ntawm dej (m) = 50 grams

Kub dej pib (T)₂= 29,8 TZS^oC

Qhov kub tshwj xeeb ntawm dej = 1 cal.g^-1.^oC^-1

Qhov kub kawg ntawm lub cev (T) = 37^oC

Nug: Cov cua sov tshwj xeeb ntawm cov hlau (c)

Lus teb:

Txoj cai dub hais tias qhov kub uas tso tawm = qhov kub uas nqus tau. Qhov kub raug tso tawm los ntawm lub npib thiab qhov kub raug nqus los ntawm dej, kom txog thaum qhov sib npaug ntawm qhov kub thiab txias raug ncav cuag.

Txhua chav ntsuas yog qhia ua grams yog li tsis tas yuav hloov cov chav ntsuas.

Q _tawm = Q _{nqus tau}

m_logam c ΔT = m_{huab cua} c ΔT

(50)(c)(85-37) = (50)(1)(37-29,8)

(50)(c)(48) = (50)(7,2)

(50)(c)(48) = (50)(7,2)

(c)(48) = 7,2

c = 7,2 / 48

c = 0,15 cal.g^-1.^oC^-1

13. Tooj liab hlau ntawm qhov kub ntawm 100^oC muab tso rau hauv dej nrog qhov hnyav ntawm 128 grams thiab qhov kub ntawm 30 ^oC. Qhov kub tshwj xeeb ntawm dej 1 cal.g^{-1 o}C^-1 thiab qhov kub tshwj xeeb ntawm tooj liab yog 0,1 cal.g^{-1 o}C^-1Yog tias qhov sib npaug ntawm qhov kub thiab txias tshwm sim ntawm qhov kub ntawm 36 ^oC, ces qhov hnyav ntawm cov hlau yog ....

A. 140 grams
B. 120 grams
C. 100 grams
D. 80 grams
E. 75 grams

Kev Sib Tham
Nws paub tias:
Kub ntawm tooj liab (T₁= 100 TZS ^oC
Cov cua sov tshwj xeeb ntawm tooj liab (c₁) = 0,1 cal.g^{-1 o}C^-1

Qhov hnyav ntawm dej (m₂) = 128 grams
Kub ntawm dej (T)₂= 30 TZS ^oC
Qhov kub tshwj xeeb ntawm dej (c₂) = 1 cal.g^{-1 o}C^-1

Qhov kub thiab txias sib npaug (T) = 36 ^oC
Lus Nug: Qhov hnyav ntawm tooj liab (m₁)
Lus teb:

Txoj cai ntawm Black hais tias qhov kub uas ib yam khoom kub siab tso tawm = qhov kub uas ib yam khoom kub qis tau txais.
Q tooj liab = Q dej
m₁ c₁ ΔT = m₂ c₂ T
(m₁)(0,1)(100-36) = (128)(1)(36-30)
(m₁)(0,1)(64) = (128)(1)(6)
(m₁)(6,4) = 768
m₁ = 768/6,4
m₁ = 120
Qhov hnyav ntawm tooj liab yog 120 grams.
Cov lus teb yog B.

14. Peb kilograms ntawm cov pas nrig dub nrog lub cua sov tshwj xeeb ntawm 1400 J.kg^-1 C^-1 kub 80^oC raug muab tso rau hauv 10 kg dej nrog qhov kub tshwj xeeb ntawm 4200 J.kg.^-1 C^-1Tom qab qhov sib npaug ntawm thermal tshwm sim, qhov kub kawg ntawm qhov sib tov yog 20^oC. Qhov kub ntawm dej pib yog….

A. 20 ^oC
B. 18 ^oC
C. 14 ^oC
D. 12 ^oC
E. 10 ^oC

Kev Sib Tham
Nws paub tias:
Qhov hnyav ntawm cov hlau lead (m₁) = 3 kg
Qhov kub tshwj xeeb ntawm tin (c₁) = 1400 J.kg^-1 C^-1
Kub ntawm cov hlau nplaum (T)₁= 80 TZS ^oC

Qhov hnyav ntawm dej (m₂) = 10 kg
Qhov kub tshwj xeeb ntawm dej (c₂) = 4200 J.kg^-1 C^-1

Qhov kub thiab txias sib npaug (T) = 20 ^oC
Xav tau: Qhov kub ntawm dej pib (T)₂)
Lus teb:
Q raug tso tawm = Q tau txais
Q tin = Q dej
m₁ c₁ ΔT = m₂ c₂ T
(3)(1.400)(80-20) = (10)(4.200)(20-T)
(4.200)(60) = (42.000)(20-T)
252.000 = 840.000 – 42.000 T
42.000 T = 840.000 – 252.000
42.000 T = 588.000
T = 588.000 / 42.000
TXL = 14
Qhov kub ntawm dej pib yog 14^oC.
Cov lus teb yog C.

15. Dej khov uas muaj qhov hnyav ntawm M grams ntawm qhov kub ntawm 0^oC, muab tso rau hauv dej uas hnyav 340 grams ntawm qhov kub ntawm 20^oC muab tso rau hauv ib lub thawv tshwj xeeb. Xav tias lub thawv tsis nqus/tso cua sov tawm. Yog tias L_es = 80 calorie g^-1, c_{huab cua} = 1 calorie g^{-1 o}C^-1, tag nrho cov dej khov yaj thiab kev sib npaug ntawm thermal ua tiav ntawm qhov kub ntawm 5^oC, ces qhov hnyav ntawm dej khov (M) yog ...

A. 60 grams
B. 68 grams
C. 75 grams
D. 80 grams
E. 170 grams

Kev Sib Tham
Nws yog paub :
Qhov hnyav ntawm dej (m) = 340 grams
Kub ntawm dej khov (T_es= 0 TZS^oC
Suhu dej (T_{huab cua}= 20 TZS^oC
Qhov kub thiab txias sib npaug (T) = 5^oC
Kub ntawm kev sib xyaw ntawm dej khov (L)_es) = 80 calorie g^-1
Qhov kub tshwj xeeb ntawm dej (c_{huab cua}) = 1 calorie g^{-1 o}C^-1
Nug Qhov hnyav ntawm dej khov (M)
Jawb :

Txoj Cai Dub hais tias nyob rau hauv ib lub kaw lus kaw uas raug cais tawm, qhov kub uas tso tawm los ntawm ib yam khoom kub siab yog tib yam li qhov kub uas nqus los ntawm ib yam khoom kub qis.
Cov cua sov uas dej tso tawm (Q tso tawm) = cov dej khov nqus cua sov (Q nqus)
m_{huab cua} c_{huab cua} (T) = m_es L_es +m_es c_{huab cua} (T)
(340)(1)(20-5) = M (80) + M (1)(5-0)
(340)(15) = 80M + 5M
5100 = 85M
M = 5100/85
M = 60 grams
Cov lus teb yog lawm yog A.

Catatan :
Yog hais tias dej khov muaj qhov kub ntawm 0^o ces cov dej tseem nyob hauv daim ntawv khov kho. Yog tias nws tau hais tias qhov kub ntawm dej yog 0^oC ces dej yog kua. Sib txawv ntawm kev siv cov lus dej khov thiab dej. Vim tias dej tseem nyob hauv daim ntawv khov lossis khov, qhov cua sov uas nqus ua ntej yog siv los yaj tag nrho cov dej khov rau hauv dej, yog li ntawm sab xis ntawm kab zauv saum toj no, ib daim ntawv qhia tau ntxiv los xam qhov cua sov kom yaj cov dej khov (m_es L_es). Tom qab tag nrho cov dej khov tau yaj mus ua dej, cua sov ntxiv yog siv los tsa qhov kub ntawm cov dej khov los ntawm 0^oC dhau los ua 5^oC.

Qhov chaw nug lus:

Cov Lus Nug Txog Kev Xeem Physics Hauv Tebchaws Rau Tsev Kawm Ntawv Theem Siab/Tsev Kawm Ntawv Theem Siab Ua Haujlwm