Thursday
December 8, 2016

Homework Help: physics

Posted by nicole on Monday, December 11, 2006 at 2:56pm.

(a) 2.0 kg of molten copper at its melting point of 1083 ºC (the copper is 100% liquid) is poured into
a mold in a cooling water bath at 20 ºC. What mass of water is needed to bring the solidified
copper and water to an equilibrium temperature of 30 ºC, assuming the only heat exchange is
between the copper and water.
(Lf copper = 1.34 x 105 J/kg, ccopper = 387 J/kg ºC, cwater = 4186 J/kg ºC)


(b) The molten copper is poured into a rod shaped mold 2 cm in radius and 18 cm long. After
cooling from 1083 ºC to 30 ºC will the rod fit inside a ring with an interior radius of 1.95 cm?
(α = 17 x 10-6 1/ºC, assume the coefficient of expansion is constant over the full temperature
range)

part a.
(mass Cu*Lf Cu) + (massH2O*LfH2O*(deltaT)= 0
solve for mass H2O.

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