B.4 Thermodynamics (HL) Flashcards
Internal Energy (U)
Total energy contained by a system’s particles due to their motion and position
Work Done (W)
Energy transferred to or from a system when a force moves an object through a distance
ΔU in Ideal Gas
Change in internal energy of an ideal gas depends on the number of particles and temperature change
PV Diagram
Graph showing the relationship between a system’s pressure (P) and volume (V), where work done is the area under the curve
First Law of Thermodynamics
Energy within a closed system is conserved: ΔU = Q - W
Q = ΔU + W
Heat added to a system equals the change in internal energy plus the work done by the system
Closed System
A system that exchanges energy but not matter with its surroundings
Adiabatic Process
A thermodynamic process with no heat exchange with the surroundings
Isothermal Process
Process at constant temperature, implying ΔU = 0 for an ideal gas
Isochoric Process
Process at constant volume, meaning no work is done (W = 0)
Entropy (S)
Measure of disorder or randomness in a system, related to the number of possible microstates
Second Law of Thermodynamics
Total entropy of an isolated system can never decrease over time.
Microstates (Ω)
The number of possible configurations that a system can have
ΔS = ΔQ/T
Change in entropy is the heat added to the system divided by the temperature
Entropy and Isolated Systems
Entropy of an isolated system not in equilibrium almost always increases
Heat Engine
A system that converts thermal energy into mechanical work
Efficiency (η)
Ratio of useful work output to heat input, η = W/Qh
Carnot Cycle
A theoretical cycle that is the most efficient reversible cycle possible between two heat reservoirs
Qh = W + Qc
Heat from the hot reservoir equals work done plus heat to the cold reservoir
Carnot Efficiency
Maximum possible efficiency of a heat engine, ηCarnot = 1 - Tc/Th
