1) The temperature of a solid is brought to the melting point. While the solid i
ID: 1641120 • Letter: 1
Question
1) The temperature of a solid is brought to the melting point. While the solid is melting,
a) the temperature remains the same until it is melted.
b) the molecules in the liquid have a higher kinetic energy than those in the solid.
c) the molecules in the solid aren’t moving until they enter the liquid phase.
d) The heat added all goes to increased kinetic energy of molecules in the liquid phase.
2) The power flux of a new star is determined to be around 16 times that of the sun. [The power flux is the power emitted per square meter of surface.] This means that the temperature of the new star is about how many times that of the Sun?
a) 16x b) 4x c) 2x d) not possible to determine.
3) A process is known to be spontaneous. This means that
a) entropy for the process must increase.
b) if the process happens while isolated, entropy for the process must increase.
c) entropy must increase only if the process is adiabatic.
d) the net heat transferred must be negative.
4) An inventor has submitted a patent claim for an engine with an efficiency which is 10% greater than the efficiency of the Carnot cycle operating between the same two temperatures. The laws of thermodynamics
a) allow this if the process wastes less heat than the Carnot cycle.
b) forbid this because Carnot was an authority on efficiency.
c) won’t allow it based on entropy production.
d) require that such an engine draw energy from another, entropy-producing process.
Explanation / Answer
1. a) the temperature remains the same until it is melted.
2. c) 2x
3. c) entropy must increase only if the process is adiabatic.
4. a) allow this if the process wastes less heat than the Carnot cycle.
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