A 100 W heater is used to boil 0.7 water at 20oC in a wok. Given that the specific heat capacity of water is 4200 Jkg-1oC-1 and the specific latent heat of vaporization of water is 2260 kJkg-1.
(a) Find the time it takes to raise the water to 100oC.
(b) Explain briefly whether the water and steam will be affected, if another heater of power 120 W is used.
(c) Calculate the amount of steam generated after the water boils for 10 minutes with the use of 100 W heater.
(d) "It should need less time to cook the food if we use steam at 100oC instead of water at 100oC." Comment on this statement.
Thank you very much~ XD
F4 physics (heat)
2008-11-16 6:24 am
回答 (2)
2008-11-16 6:47 am
✔ 最佳答案
a)Pt=mct1000t=0.7*4200*(100-20)
t=2352s
b)Reduce the time to raise the water to 100oC.
c)pt=mct+ml
100*10*60=0.7*4200*80+m2260
m=-77.5kg
d)It is correct.It is because the internal energy of steam is higher than water.
2008-11-17 1:25 am
a)∵P=mc△t
∴1000t=0.7×4200×(100-20)
t=2352s
b)so the water to 100℃
c)pt=mct+ml
100×10×60=0.7×4200×80+(m×2260)
∴m=-77.5kg
d)It is correct.It is because the internal energy of steam is higher than water.
∴1000t=0.7×4200×(100-20)
t=2352s
b)so the water to 100℃
c)pt=mct+ml
100×10×60=0.7×4200×80+(m×2260)
∴m=-77.5kg
d)It is correct.It is because the internal energy of steam is higher than water.
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原文連結 [永久失效]:
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