Question

Why is enthalpy an extensive property?

Answer 1

A physical quantity whose value is proportional to the size of the system it describes, or to the amount of matter in the system, is known as an extensive property. The mass of a sample, for example, is a large quantity that is determined by the amount of stuff present. The density, which is independent of the amount, is a related intense quantity. Whether you're talking about a drop of water or a swimming pool, the density of water is around 1g/mL, however the mass is different.

Complete answer:
Enthalpy (measured in units of J) is a broad characteristic since it is proportional to the number of components in the system. When expressed in kJ/mol or kJ/kg, however, it is an intense characteristic.
Because enthalpy is a measure of heat content, the higher the mass of any substance, the more heat it can retain at any given temperature and pressure. Enthalpy is defined as the integral of the heat capacity at constant pressure from absolute zero to the desired temperature, taking into account any phase shifts.
However, because we can't directly measure a system's overall enthalpy, we can only measure enthalpy changes.
The heat evolved or absorbed at constant pressure in a given reaction/process is referred to as a change in enthalpy.
At constant pressure, this change in enthalpy is now given by
$\Delta H=\Delta U+p\Delta V$Δ
The joule (J) is the SI unit for enthalpy change, and its value is determined by the number of components in the system. For a given change, the more of the substance(s) you have, the more heat may be absorbed or released. Extensive quantities, on the other hand, measure amounts that are not preserved throughout a thermodynamic transfer between a system and its surroundings. When a quantity of energy is transported from the surroundings into or out of a system as heat, a corresponding quantity of entropy in the system grows or drops, although not in the same amount as in the surrounds in a thermodynamic process.

Note:
Other systems, for which standard definitions do not offer a straightforward response, include those in which subsystems interact when they are joined. The way subsystems are organised, according to Redlich, may affect the classification of some characteristics as intensive or extensive. When two identical galvanic cells are linked in parallel, the system's voltage is equal to the voltage of each cell, but the amount of electric charge transmitted (or the electric current) is large.