1 Thermodynamic Systems and Properties Free Online FlashCards

What are a thermodynamic system and its surroundings?

A thermodynamic system is the matter or region selected for study; everything outside it is the surroundings.

What can cross the boundary of a closed system?

A closed system allows energy to cross its boundary but does not allow mass to cross.

How do boundary motion and heat transfer describe a boundary?

A rigid boundary does not move; a movable boundary can. An adiabatic boundary prevents heat transfer, while a diathermal boundary permits it. These descriptions are independent.

What is a state variable?

The state is a system’s condition as described by its properties. A state variable is a property, such as pressure or temperature, used to specify that condition.

How does an extensive property change with system size?

An extensive property depends on the amount of matter. At the same condition, doubling the amount of uniform material doubles its mass, total volume, and total internal energy.

What ideal-gas relation connects pressure, volume, and temperature?

For an ideal gas, $pV=mRT$, or $pv=RT$ in specific form. Use absolute pressure and absolute temperature in this relation.

How do property changes differ from heat and work?

A property change depends only on the initial and final states. Heat and work instead describe energy crossing a boundary during an interaction.

How do you convert Celsius temperature to kelvins?

Thermodynamic equations of state use absolute temperature in kelvins. Convert Celsius temperature using $T\,[\mathrm K]=t\,[^\circ\mathrm C]+273.15$.

What distinguishes an open system?

An open system allows both mass and energy to cross its boundary.

What makes a system isolated?

An isolated system allows neither mass nor energy to cross its boundary. It is an idealization that a well-insulated, sealed container may approximate.

What characterizes thermodynamic equilibrium?

In thermodynamic equilibrium, there are no unbalanced driving forces for change. This includes thermal, mechanical, chemical, and phase balance.

What does the state postulate require for a simple compressible substance?

For a simple compressible substance, two independent intensive properties specify an equilibrium state. In a two-phase liquid–vapor mixture, saturation temperature and pressure are linked, so another property, such as vapor quality, is needed.