Ho Utloisisa Melao-motheo ea 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, mocheso o mong o fetela moeeng. Setshelo le sona sea futhumala. Mocheso o lokolloang ke metsi a chesang ha o monyehe feela ke metsi a batang empa hape o monyeha ke moea le setshelo. 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. Thermos ke sistimi e arohaneng , kahoo ha ho mocheso o fetisetsoang moeeng kapa ho thermos. Mocheso o lokolloang ke metsi a chesang o monngoa feela ke metsi a batang ho fihlela motsoako o fihla tekanyong ea mocheso.
Molao-motheo oa Black 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.
Foromo ea motheo ea Black
Qtima =Qmonya
Tlhaloso: Qtima = mocheso o lokolloang ke ntho e nang le mocheso o phahameng, Qmonya = mocheso o monngoang ke lintho tse mocheso o tlase.
Lipotso tsa mohlala oa motheo oa Black
1. Sekotwana sa tšepe e chesang e boima ba 1 kg le mocheso oa 100 oC e kenngoa ka setshelong se nang le metsi a boima ba 2 kg le mocheso oa 20 oC. Mocheso oa ho qetela oa motsoako ke ofe? Mocheso o itseng oa tšepe = 450 J/kg Co, mocheso o itseng oa metsi = 4200 J/kg Co.
Puisano:
Hoa tsebahala :
m tšepe = 1 kg, Tmafura = 100 oC, m metsi = 2 kg, Tmoya = 20 oC, c tšepe = 450 J/kg Co, c metsi = 4200 J/kg Co.
E botsitsoe :
Motsoako oa T?
Jawab :
Tšepe e na le mocheso o phahameng ho feta metsi kahoo tšepe e ntša mocheso, metsi a monya mocheso.
(m)(c)(delta T) = (m)(c)(delta T)
(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 oC
Suhu Mocheso oa ho qetela oa motsoako oa tšepe e chesang le metsi a batang ha ka bobeli li le boemong ba tekano ea mocheso ke 24 oC.
2. Potso ea Tlhahlobo ea Naha ea Fisiks ea SMA/MA ea 2015/2016 Nomoro ea 20
Ligrama tse 75 tsa metsi mochesong oa 0 o C li kopanngoa le ligrama tse 50 tsa metsi e le hore mocheso oa motsoako e be 40 o C, kahoo mocheso oa pele oa ligrama tse 50 tsa metsi ke...
A. 125 o C
B. 120 o C
C. 110 o C
D. 100 o C
E. 80 o C
Puisano
Hoa tsebahala hore:
Boima ba metsi 1 (m1 ) = 75 dikgerama
Mocheso oa pele oa metsi 1 (T 1 ) = 0 o C
Boima ba metsi 2 (m2 ) = 50 dikgerama
Mocheso oa ho qetela oa motsoako (T) = 40 o C
Diyuniti tsa boima di a tshwana kahoo ha ho hlokahale phetoho.
Ho batloa: Mocheso oa pele oa metsi 2 (T 2 )
Karabo:
Molao-motheo oa Black o bolela hore tsamaisong e koetsoeng e arohaneng, mocheso o lokolloang ke ntho e nang le mocheso o phahameng o lekana le mocheso o monngoang ke ntho e nang le mocheso o tlase.
Q e lokollotsoe = Q e monyehile
m 1 c ( Δ T 1 ) = m 2 c ( Δ T 2 )
Mocheso o itseng oa metsi o tšoana kahoo c e tlosoa ho equation.
m 1 ( Δ T 1 ) = m 2 ( Δ T 2 )
(75)(40 – 0) = (50)(T 2 – 40)
(75)(40) = (50)(T 2 - 40)
3000 = 50 T 2 – 2000
3000 + 2000 = 50 T 2
5000 = 50 T 2
T 2 = 100
Karabo e nepahetseng ke D.
3. Potso ea Tlhahlobo ea Naha ea Fisiks ea SMA/MA ea 2015/2016 Nomoro ea 20
Tšepe ea ligrama tse 200 e futhumatsoa ho fihlela ho 120 o C ebe e kenngoa ka har'a ligrama tse 100 tsa metsi mochesong oa 30 o C. Kamora ho leka-lekana, mocheso oa motsoako o fetoha 60 o C. Haeba mocheso o itseng oa metsi e le 4200 J.kg -1 o C -1 , joale mocheso o itseng oa tšepe ke...
A. 10,5 J.kg -1o C -1
B. 105 J.kg -1o C -1
C. 150 J.kg -1o C -1
D. 1050 J.kg -1o C -1
E. 1500 J.kg -1o C -1
Puisano
Phetoho ea liyuniti tsa boima ho tloha ho ligrama ho ea ho lik'hilograma (Sistimi ea Machaba ea Liyuniti)
Hoa tsebahala hore:
Boima ba tšepe (m 1 ) = digrama tse 200 = 0,2 kg
Mocheso oa tšepe (T 1 ) = 120 o C
Boima ba metsi (m2 ) = digrama tse 100 = 0,1 kg
Mocheso oa metsi (T 2 ) = 30 o C
Mocheso oa ho qetela oa motsoako (T) = 60 o C
Mocheso o itseng oa metsi (c 2 ) = 4200 J.kg -1 o C -1
E botsitsoe: Mocheso o itseng oa tšepe (c 1 )
Karabo:
Q e lokollotsoe = Q e monyehile
m1 c1 (ΔT1) = m2 c2 (ΔT2)
(0,2)(c 1 )(120 – 60) = (0,1)(4200)(60 – 30)
(0,2)(c 1 )(60) = (0,1)(4200)(30)
12 c 1 = 12600
c 1 = 12600 / 12
c 1 = 1050
Karabo e nepahetseng ke D.
4. Lipotso tsa Tlhahlobo ea Naha ea SMA/MA ea 2018
250 ml ea metsi a belang (100 o C) e tšeloa ka paneng e nang le 400 ml ea metsi mochesong oa 35 o C. Kamora hore tekano ea mocheso e be teng, mocheso oa motsoako ke… (mocheso o itseng oa metsi 1,0 cal.gr -1 . o C -1 )
Puisano
Hoa tsebahala:
Mocheso oa metsi a chesang = 100 o C
Bophahamo ba metsi a chesang = 250 ml = 0,25 litre = 0,25 dm 3 = (0,25)(1000 cm 3 ) = 250 cm 3
Mocheso oa metsi a batang = 35 o C
Bophahamo ba metsi a batang = 400 ml = 0,4 litre = 0,4 dm 3 = (0,4)(1000 cm 3 ) = 400 cm 3
Mocheso o itseng oa metsi = 1,0 cal.gr -1 . o C -1
Boima ba metsi = 1 gr/ cm3
E botsitsoe: Mocheso oa motsoako
Karabo:
Bala boima ba metsi a chesang le a batang u sebelisa foromo ea bongata:
m = ρ V
m = boima, ρ = bongata, V = bophahamo
Boima ba metsi a chesang: m = ρ V = ( 1 gr/cm 3 )(250 cm 3 ) = 250 dikgerama
Boima ba metsi a batang: m = ρ V = ( 1 gr/cm 3 )(400 cm 3 ) = 400 dikgerama
Bala mocheso oa motsoako o sebelisa foromo ea molao-motheo ea Black:
Mocheso o monngoang ke metsi a batang = mocheso o lokolloang ke metsi a chesang
mc Δ T = mc Δ T
Mocheso o itseng o tšoana kahoo o tlosoa ho equation.
m Δ T = m Δ T
(400)(T-35) = (250)(100-T)
400T – 14000 = 25000 – 250T
400T + 250T = 25000 + 14000
650T = 39000
T = 39000 / 650
T = 60 o C
