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Vocab for Systems and Properties
systems and properties
24
Chemical Engineering
Undergraduate 1
02/25/2013

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Term
Open System
Definition
both matter and energy are transferred
essentially a FLOW system

tip: open > open door. can walk through it
Term
Closed System
Definition
only energy (but NOT matter) can be transferred

tip: a closed door does not mean that noises cannot be heard on the other side
Term
Isolated System
Definition
neither energy NOR matter can be transferred

tip: "isolated" > like solitary confinement. No communication and no leaving.
Term
Universe
Definition
All matter and space
Term
System
Definition
the part of the universe under our direct consideration and contains ALL the matter and space DIRECTLY involved in the process under study
Term
Surroundings
Definition
The system and surroundings are separated by a BOUNDARY that may be real or imaginary
Term
Diathermal
Definition
uninsulated- energy can be transferred across the boundary

tip: "di" > two, "thermal" > heat.
there are two heats to consider
Term
Extensive Property
Definition
depending on system size. typically depicted with uppercase letters.
e.g: mass and volume

tip: extensive > "external"
Term
Intensive Property
Definition
independent of system size
intensive properties with corresponding extensive properties are depicted with lower case letters
e.g: molar and specific volume, pressure, temperature

tip: in > "inside"
"it's what's on the inside that counts"
Term
Macroscopic scaling
Definition
describes bulk observations visible to the naked eye. A macroscopic change for a variable has the prefix: Δ
Term
Microscopic scaling
Definition
scaling describes differential volume elements NOT visible to the naked eye but containing sufficient matter to be treated as continuum. Prefix: d or δ
Term
Molecular scaling
Definition
describes individual atoms, ions, and molecules and is NOT representative of a continuum.
Term
Isothermal
Definition
processes occur at constant temperature
The system is at the same temperature as the surroundings
ex. system kept in a water bath

tip: iso > "same"
Term
Isobaric
Definition
processes occur at constant pressure
The system is kept at the same pressure by the surroundings
ex. in a flexible container or a piston-cylinder
Term
Isochoric
Definition
processes occur at constant volume
The system is in a rigid container
Term
Mechanical Equilibrium
Definition
A system is at the same pressure as the surroundings
Term
Thermal Equilibrium
Definition
A system is at the same temperature as the surroundings
Term
Equilibrium
Definition
The STATE of the system (i.e. the intensive properties pressure, molar volume, and temperature) does NOT change with time. There is no NET driving force for change

only used to describe closed and isolated systems
Term
0th Law of Thermodynamics
Definition
if two systems are both in thermal equilibrium with another system then those two systems must also be in thermal equilibrium with each other

tip: if A = B and B = C then A = C
Term
1st Law of Thermodynamics
Definition
Heat and Work are forms of energy transfer. All the energy must be accounted for as heat, work, chemical, etc. work cannot be done without energy.

tip: "you cannot get something for nothing"
Term
2nd Law of Thermodynamics
Definition
An isolated system will spontaneously move towards a state of equilibrium. Thus it achieves maximum entropy.

tip: "you cannot get back to the start because entropy (disorder) always increases"
Term
3rd Law of Thermodynamics
Definition
The entropy of a system approaches a constant value as the temperature approaches zero. Because absolute zero is unattainable:

tip: "You cannot get out of the game"
Term
Entropy
Definition
A measure of how much the energy in a system "spreads out" from the initial to the final state of a process
Maximum entropy of a system is achieved at equilibrium
Term
Enthalpy
Definition
Energy contained in molecular bonds
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