To measure the specific heat in the liquid phase of a newly developed cryoprotectant, you place a sample of the new cryoprotectant in contact with a cold plate until the solution’s temperature drops from room temperature to its freezing point. Then you measure the heat transferred to the cold plate. If the system isn’t sufficiently isolated from its room-temperature surroundings, what will be the effect on the measurement of the specific heat? (a) The measured specific heat will be greater than the actual specific heat; (b) the measured specific heat will be less than the actual specific heat; (c) there will be no effect because the thermal conductivity of the cryoprotectant is so low; (d) there will be no effect on the specific heat, but the temperature of the freezing point will change.
To measure the specific heat in the liquid phase of a newly developed cryoprotectant, you place a sample of the new cryoprotectant in contact with a cold plate until the solution’s temperature drops from room temperature to its freezing point. Then you measure the heat transferred to the cold plate. If the system isn’t sufficiently isolated from its room-temperature surroundings, what will be the effect on the measurement of the specific heat? (a) The measured specific heat will be greater than the actual specific heat; (b) the measured specific heat will be less than the actual specific heat; (c) there will be no effect because the thermal conductivity of the cryoprotectant is so low; (d) there will be no effect on the specific heat, but the temperature of the freezing point will change.
To measure the specific heat in the liquid phase of a newly developed cryoprotectant, you place a sample of the new cryoprotectant in contact with a cold plate until the solution’s temperature drops from room temperature to its freezing point. Then you measure the heat transferred to the cold plate. If the system isn’t sufficiently isolated from its room-temperature surroundings, what will be the effect on the measurement of the specific heat? (a) The measured specific heat will be greater than the actual specific heat; (b) the measured specific heat will be less than the actual specific heat; (c) there will be no effect because the thermal conductivity of the cryoprotectant is so low; (d) there will be no effect on the specific heat, but the temperature of the freezing point will change.
Geologists measure conductive heat flow out of the earth by drilling holes (a few hundred meters deep) and measuring the temperature as a function of depth. Suppose that in a certain location the temperature increases by 20°C per kilometer of depth and the thermal conductivity of the rock is 2.5 W/m·K. What is the rate of heat conduction per square meter in this location? Assuming that this value is typical of other locations over all of earth's surface, at approximately what rate is the earth losing heat via conduction? (The radius of the earth is 6400 km.)
Ice of mass 12.8 kg at 0°C is placed in an ice chest. The ice chest has 2.7 cm thick walls of thermal conductivity 0.07 W/m·K and a surface area of 1.29 m2. Express your answers with appropriate mks units.
(a) How much heat must be absorbed by the ice during the melting process?
(b) If the outer surface of the ice chest is at 39° C, how long will it take for the ice to melt?
The concrete slab of a basement is 11 m long and 8 m wide, and 0.20 m thick. During the winter, temperatures are
nominally 17°C and 10°C at the top and bottom surfaces, respectively. If the concrete has a thermal conductivity of 1.4
W/mK, what is the rate of heat loss through the slab? If the basement is heated by a gas furnace operation at an
efficiency of 90%, and natural gas is priced at $0.02. MJ, what is the daily cost of the heat loss.
Answer: QLOSS = 4.312 kW, COST = $8.28/day
Chapter 17 Solutions
University Physics with Modern Physics (14th Edition)
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