Conceptual questions
Temperature is a measure of the
a. Total kinetic energy of a system
b. Total potential energy of a system
c. Average energy per particle of a system
d. Maximum energy of a particle in a system
c
5233 J of heat flows into 0.25 kg of water. What is the increase in temperature of the water in C?
c = 4,186 J/kg C
5 C
A gas system starts with 500J of thermal energy. Then the gas has 50 J of work done on it. The gas also gives 20J of heat to its environment. What is the final thermal energy of the gas?
530J
0.2kg of water at 23C is combined with 0.2kg of water at 73C. What is the equilibrium temperature assuming the system is closed?
48C
A heat pump
a. makes heat flow from a colder region to a hotter region spontaneously
b. makes heat flow from a hotter region to a colder region spontaneously
c. makes heat flow from a hotter region to a colder region by doing work
d. makes heat flow from a colder region to a hotter region by doing work
Heat is a measure of the
a. Potential energy of a system
b. Thermal energy transferred to a system
c. Kinetic energy of a system
d. Number of particles transferred to a system
b
How many kg of water can be heated up by 10C by 25,120J of heat?
c = 4,186 J/kg C
0.6kg
A system of gas does 40J of work on its environment. The gas ends up gaining 30J of internal thermal energy. How much heat flowed into the gas?
70J
0.4kg of water at 20C is combined with 0.2kg of water at 80C. What is the equilibrium temperature assuming the system is closed?
40C
A 2kg piece of metal has a specific heat capacity of 900 J/kg C. How much heat must flow into the metal to raise its temperature by 10C?
18,000J
What are the 3 ways of transferring heat?
Give an example of each.
Conduction, Convection, Radiation
A Joule apparatus allows a 50kg mass to fall down and heats up a 0.49kg system of liquid (c=500 J/kg C) by 3C. How far did the 50kg mass fall?
1.5m
A heat engine takes in 70J of heat and does 20J of work. The engine gains 15J of internal energy. How much heat was lost to the environment?
35J
0.5kg of water at 13C is combined with 0.9kg of water at 88C. What is the equilibrium temperature assuming the system is closed?
61.2C
The gas from a rocket engine is typically higher than the melting point of the metal of the engine. What are two ways the engineers can keep the rocket from melting?
regenerative cooling (fuel flowing heat away) and insulating cooler air buffer
What makes something a heat engine?
How is the efficiency of a heat engine defined?
Transforms heat into mechanical energy
eff = W/Qh
An engine has 50,000J of work done on it, but the internal energy of the engine increases only by 19,860J since it lost some heat to a 4kg bath of water (c=4186J/kg C) it was sitting in. How much did the water temperature increase by?
1.8C
A heat engine uses 500J of heat and does 100J of work. What was the efficiency of the engine?
0.2
0.5kg of water at 30C is combined with oil at 80C. If the equilibrium temperature reached is 65C, what was the mass of the oil?
c water = 4186 J/kgC
c oil = 2093 J/kg C
2.33kg
A 0.6kg piece of metal has a specific heat capacity of 555 J/kg C and starts at a temperature of 40C. If 50,000J of heat flows into the metal, what is the final temperature of the metal?
190C
What does the "heat death of the universe" refer to?
2nd law of thermodynamics states heat flows from hot to cold and so energy becomes less and less organized and less useful. Once equilibrium is reached no more heat flow will occur.
A 0.2 kg piece of plastic at initial T=80C has a specific heat of 500 J/kg C and is set in a 0.6kg cup of water (c=4186 J/kg C) at 20C. If the system is closed and isolated, what is the equilibrium temperature reached by the system?
22.3C
A heat engine does 300J of work and loses 200J of energy to the environment. What was the efficiency of the heat engine?
0.6
0.2kg of water at 30C is combined with 0.2kg of oil at 80C. What is the equilibrium temperature assuming the system is closed?
c water = 4186 J/kgC
c oil = 2093 J/kg C
46.6C
An engine with a mass of 20kg has an initial temperature of 15C and takes in 35,000J of heat energy. The engine does 20,000J of work. The rest of the energy stays in the heat engine which has a specific heat capacity of 600 J/kg C. What is the final temperature of the engine?
16.25C