Thermodynamics — Definition of an Isolated System In an isolated thermodynamic system, neither heat nor work crosses the system boundary, and no mass transfer occurs. Evaluate the statement: “In an isolated system, neither heat and work nor the mass of the working substance crosses the boundary of the system.”

Introduction / Context:
Thermodynamic systems are categorized by what can cross their boundaries. The strictest case is an isolated system, a cornerstone concept for applying conservation laws and the second law to the “universe” comprising system plus surroundings.

Given Data / Assumptions:

• System boundary is perfectly adiabatic (no heat transfer).
• Boundary is perfectly rigid and non-working (no shaft/boundary work or any other work mode).
• No mass can enter or leave the system control mass.

Concept / Approach:
By definition, an isolated system exchanges neither energy nor matter with its surroundings. Energy exchanges include heat (Q) and work (W) of any kind (shaft, electrical, boundary). Therefore, for an isolated system over any process: Q = 0, W = 0, and mass_in = mass_out = 0.

Step-by-Step Solution:
Identify what the statement claims: no heat, no work, and no mass across the boundary.Recall the formal definition of an isolated system: no interaction at all with surroundings in terms of energy or matter.Match the two: the statement precisely restates the definition of an isolated system.

Verification / Alternative check:
Considering the “system + surroundings” as an isolated whole (the universe) helps verify that internal exchanges may occur within subsystems, but nothing crosses the overarching isolated boundary. Classic examples include an idealized, perfectly insulated, sealed rigid tank undergoing internal mixing with no external connections.

Why Other Options Are Wrong:
“False” would allow some combination of heat, work, or mass transfer, contradicting the strict definition of an isolated system.

Common Pitfalls:
Confusing “closed” systems (no mass but possible heat/work) with “isolated” systems. Another confusion is assuming only heat is blocked; in isolation, both heat and all forms of work are prevented.

Final Answer:
True