Thermodynamics and Gases Flashcards
What is internal energy?
The sum of all energies of all the molecules in a substance.
What is temperature?
Related to the average kinetic energy per molecule of a substance.
What is power?
Work per time.
What is conduction?
The physical transfer of atomic vibration energy from one atom to another.
What is convection?
Convectionn is the transfer of thermal energy fromm one place to another through fluid flow.
What is radiation?
The transfer of energy through electromagnetic waves.
What is the first law of thermodynamics?
A statement of conservation of energy.
ΔU = Q + W
What is the sign of Q is heat is added to a gas?
Positive
What is the sign of Q is heat is taken from a gas?
Negative
What happens to ΔU if the internal temperature of a gas rises?
ΔU is positive
What does positive W mean?
Work is done ON a gas
What does negative W mean?
Work is done by a gas. An example would be a gas’s volume increasing.
What does a higher PV mean in terms of temperature?
The temperature will be higher. This is due to PV=nRT
What is an isothermal line?
The lines on a P vs V graph, which have the same value of PV. Because these points have the same PV they also share the same T.
What shape does an isothermal line make?
A hyperbola
What does moving to the right on a P vs V graph mean?
Negative work
What does moving to the left on a P vs V graph mean?
Positive work
What happens when you move up or down on a P vs V graph?
No work is done, as the volume does not change. Work requires motion.
How is work related to pressure and volume mathematically?
W = -PΔV
What does the area under a P vs V graph mean?
A larger area means a larger magnitude of work has been done.
What is the temperature change in a cycle?
0, as temperature change relies on PV. If PV doesn’t change, neither does T.
How does one find the net work in a cycle?
By finding the area INSIDE of the cycle.
What are the four special processes on a PV diagram?
Isobaric, Isochoric/Isovolumetric, Isothermal, and Adiabatic
When is a path isobaric?
When pressure remains the same.
What does an isobaric path look like?
The graph moves left or right.
When is a path Isochoric/Isovolumetric?
When volume remains constant.
What does an isochoric/isovolumetric path look like?
The graph moves up or down.
When is a path adiabatic?
No heat transfer between the system and the enviroment takes place.
What does an adiabatic path look like?
Curved path, similar to isothermal but steeper.
What is the second law of thermodynamics?
The entropy of a system cannot decrease unless work is done on that system.
What is entropy?
A thermodynamic quantity representing the unavailability of a system’s thermal energy for conversion into mechanical work, often interpreted as the degree of disorder or randomness in the system.
