3.1

Front: What is a thermodynamic system?
Back: A thermodynamic system includes anything whose thermodynamic properties are of interest.
Front: What separates a thermodynamic system from its surroundings?
Back: A boundary, which is an imagined wall between the system and the environment.
Front: Define an open system.
Back: An open system is one that can exchange both energy and matter with its surroundings.
Front: Define a closed system.
Back: A closed system (or isolated system) is completely separated from its environment and cannot exchange energy or matter.

Front: What defines thermal equilibrium?
Back: Thermal equilibrium is reached when the temperature is the same across different objects in contact and net heat transfer is zero.
Front: State the Zeroth Law of Thermodynamics.
Back: If object 1 is in thermal equilibrium with objects 2 and 3, then objects 2 and 3 must also be in thermal equilibrium with each other.
Front: What is the mathematical expression for the Zeroth Law?
Back: If $T_1 = T_2$ and $T_1 = T_3$, then T_2 = T_3.

Front: What is an equation of state?
Back: It is the relationship between a system's pressure, volume, and temperature, written symbolically as $f(p, V, T) = 0$.
Front: Define an extensive variable.
Back: An extensive variable (like volume or total energy) doubles its value if the amount of matter in the system doubles.
Front: Define an intensive variable.
Back: Intensive variables (like pressure or temperature) do not change their value based on the amount of matter in the system.