### 1st Law of Thermodynamics

Each list begins with basic conceptual vocabulary you need to know for MCAT questions and proceeds to advanced terms that might appear in context in MCAT passages. The terms are links to Wikipedia articles.
Thermodynamics
Thermodynamics is a branch of physics that studies the effects of changes in temperature, pressure, and volume on physical systems at the macroscopic scale by analyzing the collective motion of their particles.
First law of thermodynamics
The first law of thermodynamics states that the increase in the internal energy of a thermodynamic system is equal to the amount of heat energy added to the system minus the work done by the system on the surroundings.
Conservation of energy
The conservation of energy states that the total amount of energy in any system remains constant, although it may change forms.
Mechanical work
Mechanical work is the amount of energy transferred by a force.
Isothermal process
An isothermal process is a thermodynamic process in which the temperature of the system stays constant.
Heat transfer
Heat transfer is the passage of thermal energy from a hot to a cold body.
Internal energy
The internal energy of a thermodynamic system is the total of the kinetic energy due to the motion of molecules and the potential energy associated with the vibrational and electric energy of atoms within molecules or crystals.
Isolated system
An isolated system, as contrasted with a open system, is a physical system that does not interact with its surroundings.
Isobaric process
An isobaric process is a thermodynamic process in which the pressure stays constant.
Isochoric process
An isochoric process, also called an isometric process or an isovolumetric process, is a thermodynamic process that occurs without a change in volume.
An adiabatic process or an isocaloric process is a thermodynamic process in which no heat is transferred to or from the working fluid.
Thermodynamic system
A thermodynamic system, originally called a working substance, is defined as that part of the universe that is under consideration, separated by a real or imaginary boundary from the environment or surroundings
Thermodynamic state
A thermodynamic state is the macroscopic condition of a thermodynamic system as described by its particular thermodynamic parameters.
Thermodynamic process
A thermodynamic process may be defined as the evolution of a thermodynamic system proceeding from an initial state to a final state.
Mechanical equivalent of heat
The mechanical equivalent of heat was an expression of 19th century science stating that mechanical work may be transformed into heat, and conversely heat into work, with the magnitude of one always proportional to the other.
Work
In thermodynamics, work is the quantity of energy transferred from one system to another without an accompanying transfer of entropy.
State function
A state function is a property of a system that depends only on the current state of the system, not on the way in which the system got to that state.
Open system
A open system describes a system in continuous interaction with its environment.
Closed system
A closed system can exchange heat and work with its surroundings but not matter. This is in contrast to an isolated system which can exchange neither heat nor matter with the surroundings.
Phenomenological thermodynamics
Phenomenological thermodynamics is a branch of thermodynamics concerned with the study and analysis of actual phenomena without evaluation of statistical energy-level atomic and molecular details.
Polytropic process
A polytropic process is a thermodynamic process in which the logarithm of the pressure versus the logarithm of the volume is a straight line.

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