Q1: Many Chinese foods are cooked by steam cookers. Steam cookers heat food by condensing steam on it. One such cooker supplies steam at 110℃ at the rate of 0.1 kh per minute. Calculate the rate, in watts, at which the steam cooker supplies heat ebergy if the steam condenses to water at 100℃. The specific heat capacity of steam is 2000J kg^-1 ℃^-1.
Q.2: Ice is added to bottel of water and the mixture is well stirred. The temperature of the mixture remains steady at 0℃ and the masses of ice and water inside the bottle are found to be 0.15kg and 0.6kg respectively. If the mixture is heated by a heater at a constant rate, and the time required to melt the ice completely is "t", what will be the temperature of the mixture after "2t"?
Q.3: 0.6kg of ice at 0℃ mixed with 0.25kg of water at 25℃. Find the final temperature of the "mixture".
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幾條Form 3 ge physics~~ plx help!! (15點,三條)
2008-06-12 6:14 am
回答 (2)
2008-06-12 4:14 pm
✔ 最佳答案
Q1. 0.1 kh per minute應該係0.1kg per minute?咁佢話明咗steam condenses to water at 100℃...
掉返轉黎諗...即係個Steam cookers 將0.1kg 100℃的水--->0.1kg110℃的steam per minute
將0.1kg 100℃的水--->0.1kg110℃的steam per minute所需的energy:
Specific Latent Heat of Vaperization is 2.26x10^6kg^-1J
0.1kg 100℃的水--->0.1kg100℃的steam
0.1X2.26X10^6=2.26X10^5J
0.1kg100℃的steam--->0.1kg110℃的steam
0.1X10X2000=2000J
加埋:2000+2.26X10^5=228000J
即係個 steam cookers提供228000J per minute
p=E/t
p=228000/60
p=3800w
Q.2
melt the ice completely is "t", 即係個heater係T時間時將0.15kg的ice熔解..
specific Latent Heat of Fusion:3.34x10^5 kg^-1J
heater係T時提供:0.15X10^5=15000J
依家就有0.15+0.6=0.75KG 0℃的水了
2T時..即係個heater提供多15000J..
0.75x4200x(t-0)=15000
t=4.76℃
Q.3由0.6kg0℃的ice 熔解晒所需要吸的energy:
0.6x3.34x10^5=200400J
由0.25kg 25℃的water轉去0℃的water所需要放的energy:
0.25x25x4200=26250J
由於0.6kg0℃的ice 能把0.25kg 25℃的water的energy吸至0度..
so the mixture is 0℃..
個mixture有0.521kg的ice和0.329kg的water
2008-06-12 19:13:19 補充：
唔該晒oblivions_tear ...
heater係T時提供:0.15X10^5x3.34=50100J
0.75x4200x(t-0)=50100
T=15.9℃
唔好意思..今朝太趕...冇CHECK到題目..
2008-06-12 8:44 pm
heater係T時提供:0.15X10^5=15000J?
收錄日期: 2021-04-13 15:40:55
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