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Topic: Thermodynamics/Law of Conservation of Energy  (Read 5284 times)

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krissypoo44

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Thermodynamics/Law of Conservation of Energy
« on: November 21, 2004, 01:19:22 PM »
If 100.0g of pure water at 27 degrees C are placed into an insualted flask, have many grams of ice at 0 degrees C must be added to lower the temperature of the water to 5 degrees C?

Offline Mitch

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Re:Thermodynamics/Law of Conservation of Energy
« Reply #1 on: November 21, 2004, 04:13:23 PM »
Please show that you have attempted the problem before posting.
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krissypoo44

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Re:Thermodynamics/Law of Conservation of Energy
« Reply #2 on: November 22, 2004, 02:19:21 PM »
i have no idea how to attempt this, other than I know it has something to do with the Law of Conservation of Energy.  We tried it with heating and cooling curves and got nowhere. Could someone at least tell us how to start? The eleven of us are stuck.

Demotivator

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Re:Thermodynamics/Law of Conservation of Energy
« Reply #3 on: November 22, 2004, 02:43:26 PM »
When water cools from 27 to 5 degrees, heat is given off which can be calculated using the heat capacity of water.
That same heat is absorbed (conservation of energy, so set up an equation) by the melting ice which after melting turns to water and has its temp raised from 0 to 5 deg. The heat of fusion for ice melting is known. The heat capacity of water that comes from the ice melt as it is raised to 5 degrees is known. The only unknown to solve for is the grams of ice.
« Last Edit: November 22, 2004, 02:45:42 PM by Demotivator »

Offline Donaldson Tan

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Re:Thermodynamics/Law of Conservation of Energy
« Reply #4 on: December 17, 2004, 11:19:10 AM »
heat lost by water = heat gain by melting ice
m1.c.dT = m2.lf

m1: mass of water
m2: mass of ice
c: specific heat capacity of water
dT: change in temperature of water
lf: latent heat of fusion for water
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