Question

Which of the following is/are macroscopic variables:
A) Volume
B) Pressure
C) Temperature
D) All of the above

Answer 1

A thermodynamic state of a system is its condition at a given moment, as defined by the values of an appropriate collection of parameters known as state variables, state parameters, or thermodynamic variables in thermodynamics. Once a set of thermodynamic variables has been established for a system, the values of all of the system's thermodynamic characteristics are determined uniquely. A thermodynamic state is usually assumed to be one of thermodynamic equilibrium by default. This means that the state isn't only the state of the system at a certain point in time; it's also the state of the system over an infinitely long period of time.

Complete answer:
Aside from the immediately observable ordinary physical variables that first define a system's thermodynamic state, state functions, also known as state variables, thermodynamic variables, state quantities, or functions of state, characterise the system. The thermodynamic state, as identified by the initial state variables, determines them in a unique way. There are several state functions of this type. When the thermodynamic state of a particular body, of a certain chemical constitution, has been fully characterised by its pressure and volume, its temperature is uniquely determined.
A macroscopic variable is a quantifiable quantity that describes the system's whole state. The state of equilibrium of a macroscopic system may be defined in terms of quantifiable characteristics such as temperature, pressure, and volume, often known as thermodynamic variables.
Therefore, option (D) is correct.

Note:
A thermodynamic system is more than just a physical one. Rather, a particular thermodynamic system is made up of an unlimited number of distinct alternative physical systems, because a physical system has many more microscopic properties than are specified in a thermodynamic description. A thermodynamic system is a macroscopic item for which the microscopic features are not explicitly taken into account in the thermodynamic description. The number of state variables needed to define the thermodynamic state varies per system and isn't always known ahead of time; it's generally discovered through experiment.