✔ 最佳答案
Let T be the final temperature
Heat released by a ice cube = (20/1000) x [330000 + 4200T] J
Heat abosbed by cup & beverage = 500 x (20-T)
Using the heat balance equation:
500 x (20-T) = (20/1000) x [330000 + 4200T]
solve for T gives T = 5.82 degree C
If two cubes are added,
Heat given out by the two ice cubes after melting = 2 x (20/1000) x 330000 J = 13200 J
Heat abosrbed by cup & beverage when their temperature fall to 0'C
= 500 x 20 J = 10000 J
Since heat provided by melting all two ice cubes (13200 J) is larger than heat requried to cool down the cup & beverage down to freezing point (10000 J), the final temperature of the mixture is at 0'C.
2011-01-03 14:02:42 補充：
Sorry...I have interchanged the word "released" and "absorded" in my answer. Heat ABSORBED by the two ice cubes on melting = 13200 J. Heat RELEASED by cup & beverage = 10000 J
2011-01-03 14:05:46 補充：
It is thus clear that the heat released by the cup & beverage is NOT SUFFICIENT to melt all ice cubes. Hence, there is still remaining pieces of ice in the mixture when the temperature of the cup & beverage has dropped to 0'C. The final temperature is thus at 0'C.
2011-01-03 14:10:01 補充：
Q:我想問汽化比潛熱的試驗中，爲什麽要用碎冰而不用塊狀的冰？
Because ice is a bad conductor of heat, crushed ice has more surface area than ice cubes and could be melted quicker
