1. Tlhaloso ea molao-motheo oa batho ba batšo
Haeba re kopanya metsi a chesang le a batang ka setshelong se bulehileng (mohlala, bakete), mocheso o fetela ho tloha metsing a chesang ho ea metsing a batang. Hobane setshelo se bulehile, joale mocheso o itseng o fetela moeeng. Setshelo le sona sea futhumala. Mocheso o lokolloang ke metsi a chesang ha o monyehe feela ke metsi a batang, empa o boetse o monyeheloa ke sepakapaka le lijana. Tabeng ena, bakete ke sistimi e sa arohaneng. Ha re kopanya metsi a chesang le a batang ka har'a thermos e koetsoeng, mocheso o fetela ho tloha metsing a chesang ho ea metsing a batang. Li-thermos ke litsamaiso tse arohaneng, kahoo ha ho mocheso o kenang moeeng kapa thermos. Metsi a batang a monya mocheso o lokolloang ke metsi a chesang feela ho fihlela motsoako oa metsi a chesang le metsi a batang o fihla tekanyong ea mocheso.
Molao-motheo o Motšo o bolela hore tsamaisong e koetsoeng e arohaneng, mocheso o lokolloang ke ntho e nang le mocheso o phahameng = mocheso o monngoang ke ntho e nang le mocheso o tlase.
2. Foromo ea molao-motheo oa batho ba batšo
Ho lokolloa ha Q = ho monngoa ha Q
Ho lokolloa ha Q = mocheso o lokolloang ke lintho tse mocheso o phahameng, ho monngoa ha Q = mocheso o monngoang ke lintho tse mocheso o tlase.
3. Mehlala ea lipotso le lipuisano
Mohlala oa bothata 1.
Tšepe e chesang e boima ba 1 kg le mocheso oa 100 o C e kenngoa ka setshelong se nang le 2 kg ea metsi le mocheso oa 20 o C. Mocheso oa motsoako oa ho qetela ke ofe? Mocheso o itseng oa tšepe = 450 J/kg Co , mocheso o itseng oa metsi = 4200 J/ kg Co.
Tse tsejoang:
Boima ba tšepe (m) = 1 kg
Mocheso oa tšepe (T) = 100 o C
Boima ba metsi (m) = 2 kg
Mocheso oa metsi (T) = 20 o C
Mocheso o itseng bakeng sa tšepe (c) = 450 J/kg C o
Mocheso o itseng bakeng sa metsi (c) = 4200 J/kg C o
Ho batloa: T?
Tharollo:
Tšepe e na le mocheso o phahameng ho feta metsi hoo tšepe e lokollang mocheso, metsi a monyang mocheso.
Ho lokolloa ha Q = ho monngoa ha Q
mc ΔT = mc ΔT
(1)(450)(100-T) = (2)(4200)(T-20)
(450)(100-T) = (8400)(T-20)
45000 – 450T = 8400 T – 168000
45000 + 168000 = 8400 T + 450 T
213000 = 8850 T
T = 213000 : 8850
T = 24 o C
Mocheso oa ho qetela oa motsoako oa tšepe e chesang le metsi a batang ha ka bobeli li le boemong ba mocheso ke 24 o C.
Mohlala oa tokollo ea 2.
Boima ba leqhoa ba 0.2 kg bo tsoakiloeng le tee e futhumetseng ka boima ba 0.2 kg. Mocheso oa leqhoa = -10 o C, mocheso oa tee e futhumetseng = 40 o C. Mocheso o itseng oa leqhoa = 2100 J/kg Co , mocheso o itseng oa metsi = 4200 J/kg Co , mocheso oa ho kopanya metsi = 334000 J/kg. Leqhoa le tee li kopantsoe tsamaisong e arohaneng, e koetsoeng.
Tse tsejoang:
Boima ba leqhoa (m) = 0.2 kg
Boima ba tee (m) = 0.2 kg
Mocheso o itseng oa metsi (c) = 4180 J/kg C o
Mocheso o itseng oa leqhoa (c) = 2100 J/kg C o
Mocheso oa ho kopanya metsi (L F ) = 334 x 10 3 J/kg
Thempereichara ea leqhoa ( leqhoa la T ) = -10 o C
Mocheso oa tee ( tee ea T ) = 40 o C
Ho batloa: Motsoako oa T
Tharollo:
Mohato oa pele, hakanya boemo ba ho qetela
Mocheso o lokelang ho ntšoa ke metsi ho fokotsa mocheso oa 0.2 kg ea tee e futhumetseng, ho tloha ho 40 oC ho isa ho 0 oC
Q release = mc ∆T
Q ho lokolloa = (0.2 kg) (4180 J/Kg Co ) (40 o C – 0 o C)
Q ho lokolloa = (0.2 kg) (4180 J/Kg Co ) (40 o C)
Q e lokollotsoe = 33,440 Joule
Q e lokolloa = 33.44 kJ
Mocheso o monngoa ke leqhoa la 0.2 kg ho eketsa mocheso ho tloha ho -10 o C ho isa ho 0 o C
Q e monyelitsoeng = mc ∆T
Q e monyetsweng = (0.2 kg) (2100 J/Kg Co ) (0 o C – (-10 o C))
Q e monyetsweng = (0.2 kg) (2100 J/Kg Co ) (10 o C)
Q e monyelitsoeng = 4,200 Joule
Q e monyehileng = 4.2 kJ
Mocheso o monngoa ho qhibilihisa leqhoa la 0.2 kg (mocheso o hlokahalang ho qhibilihisa leqhoa lohle ka metsing)
Q fusion = m L F
Q fusion = (0.2 kg) (334 x 10 3 J/kg)
Q fusion = 66.8 x 10 3 Joule
Q fusion = 66.8 kJ
Ho latela dipalo tse ka hodimo, diphetho:
Q e lokolloa = 33.44 kJ
Q monya = 4.2 kJ
Q fusion = 66.8 kJ
Ha tee e ntsha mocheso o fihlang ho 33.44 kJ, mocheso wa tee o fetoha ho tloha ho 40 o C ho ya ho 0 o C. Mocheso o mong o ntshwang (o ka bang 4.2 kJ) o sebediswa ho phahamisa mocheso wa leqhoa ho tloha ho -10 o C ho ya ho 0 o C. 33.44 kJ – 4.2 kJ = 29.24 kJ. Mocheso o setseng = 29.24 kJ. Ho qhibilihisa leqhoa lohle ka metsing ho hloka mocheso wa 66.8 kJ. Mocheso o setseng ke 29.24 kJ feela.
Qetellong, mocheso o ntshwang ke tee e futhumetseng o sebediswa feela ho phahamisa mocheso wa leqhoa ho tloha ho -10 o C ho ya ho 0 o C le ho qhibilihisa leqhoa le itseng. Leqhoa le leng le qhibilihile metsing; le leng ha le a qhibiliha. Nakong ya tshebetso ya ho fetola ntho e tiileng hore e be mokelikeli, mocheso ha o fetohe. Ka hona, mocheso wa motswako wa ho qetela = 0 o C.
Mohlala oa bothata 3.
boima ba tee e chesang (m) = 0.4 kg,
boima ba leqhoa (m) = 0.2 kg,
mocheso oa leqhoa = -10 o C
mocheso oa tee e chesang = 90 o C.
Haeba ka bobedi di kopantswe, mocheso wa motswako wa ho qetela ke ofe?
Mocheso o itseng bakeng sa metsi (c) = 4180 J/kg Co2 ,
Mocheso o itseng bakeng sa leqhoa (c) = 2100 J/kg Co2 ,
Mocheso oa ho kopanya metsi (L F ) = 334 x 103 J/kg
Tharollo:
Mohato oa pele: Hakanya boemo ba ho qetela
Mocheso o lokelang ho ntšoa ke metsi ho fokotsa mocheso oa 0.4 kg ea tee e chesang, ho tloha ho 90 o C ho isa ho 0 o C
Q release = mc ∆T
Q ho lokolloa = (0.4 kg) (4180 J/Kg Co ) (90 o C – 0 o C)
Q ho lokolloa = (0.4 kg) (4180 J/Kg Co ) (90 o C)
Q e lokollotsoe = 150,480 Joule
Q e lokolloa = 150.48 kJ
Mocheso o monngoang ke leqhoa la 0.2 kg ho eketsa mocheso oa lona ho tloha ho -10 o C ho isa ho 0 o C
Q e monyelitsoeng = mc ∆T
Q e monyetsweng = (0.2 kg) (2100 J/Kg Co ) (0 o C – (-10 o C))
Q e monyetsweng = (0.2 kg) (2100 J/Kg Co ) (10 o C)
Q e monyelitsoeng = 4,200 Joule
Q e monyehileng = 4.2 kJ
Mocheso o ne o hlokahala ho qhibilihisa leqhoa la 0.2 kg (mocheso o ne o hlokahala ho fetola leqhoa lohle hore e be metsi)
Q fusion = m L F
Q fusion = (0.2 kg) (334 x 10 3 J/Kg)
Q fusion = 66.8 x 10 3 Joule
Q fusion = 66.8 kJ
Ho latela dipalo tse ka hodimo, diphetho:
Q e lokolloa = 150.48 kJ
Q e monyehileng = 4.2 kJ
Q fusion = 66.8 kJ
Ha tee e chesang e ntša mocheso oa 150.48 kJ, mocheso oa tee e chesang o ile oa fetoha ho tloha ho 90 o C ho ea ho 0 o C. Mocheso o mong o lokollotsoeng (o ka bang 4.2 kJ) o ile oa sebelisoa ho phahamisa mocheso oa leqhoa ho tloha ho -10 o C ho ea ho 0 o C.
150.48 kJ – 4.2 kJ = 146.28 kJ. Mocheso o setseng = 146.28 kJ.
Mocheso o hlokahalang ho qhibilihisa leqhoa lohle ka metsing ke 66.8 kJ feela. 146.28 kJ – 66.8 kJ = 79.48 kJ. Ho ile ha fumaneha hore e eketsehileng e ne e le 79.48 kJ. Tee e chesang ha e lokolle mocheso oohle ho fihlela mocheso o theohile ho 0 o C. Qeto: mocheso oa motsoako oa ho qetela o tlameha ho ba moholo ho feta 0 o C.
Mohato oa Bobeli: Fumana mocheso oa ho qetela (T)
Mocheso o hlokahalang ho eketsa mocheso oa leqhoa ho tloha ho -10 o C ho isa ho 0 o C = 4200 Joules
Mocheso o ile oa tlameha ho qhibilihisa leqhoa lohle ka metsing, hape e le mocheso o patiloeng = 66,800 Joules
Mocheso o ne o lokela ho eketsa mocheso oa metsi (metsi a tsoang ho motsoako oohle oa leqhoa) ho tloha ho 0 o C ho ea ho T = (boima ba leqhoa) (mocheso oa metsi) (T – 0 o C) = (0.2 kg) (4180 J/kg Co ) (T) = (836 T) J/C o
Mocheso o ntshwang ke tee e futhumetseng ho fokotsa mocheso ho tloha ho 90 o C ho ya ho T = (boima ba metsi a chesang) (mofuta wa mocheso wa metsi) (90 o C – T) = (0.4 kg) (4180 J/kg Co ) (90 o C – T) = 1672 J/C o (90 o C – T) = 150,480 J – (1672 T) J/C o
4200 J + 66,800 J + (836 T) J/C o = 150,480 J – (1672 T) J/C o
71,000 J + (836 T) J/C o = 150,480 J – (1672 T) J/C o
(836 T) J/C o + (1672 T) J/C o = 150,480 J – 71,000 J
(2508 T) J/C o = 79,480 J
T = 31.7 o C
Mocheso oa ho qetela = 31.7 o C
