A freezer contains 20 kg of food with a specific heat of 2 x 10^3 J/kgC. The freezer motor then operates for 10 minutes reducing the temperature to -8 degrees Celsius.
a) How much heat is removed from the food during this time? The freezer motor operates at 400 watts.
b) How much energy is delivered to the freezer motor during the 10 minute period?
c) During this time, how much total heat is ejected into the room in which the freezer is located?
d) Determine the temperature change in the room if the specific heat of air is 700 J/kgC. Assume there are 80 kg of air in the room, the volume of the air is constant, and there is no heat loss from the room.
2 answers
I will be happy to critique your thinking.
(a) Q1 =(sp,heat)(grams)(T1-T2)
I think the initial temperature, T1, should be given. As it stands, we have two unknowns, Q1 and T1.
(b) Q2 = (watts)(seconds)
(c) Q3 = Q2-Q1
(d) Q3 = (sp.heat of air)(grams air)(∆T)
Substitute values from previous steps, solve for (∆T)
I think the initial temperature, T1, should be given. As it stands, we have two unknowns, Q1 and T1.
(b) Q2 = (watts)(seconds)
(c) Q3 = Q2-Q1
(d) Q3 = (sp.heat of air)(grams air)(∆T)
Substitute values from previous steps, solve for (∆T)