1st Law of Thermo


SYSTEM: Region being considered, usually enclosed in a boundary

SURROUNDING: Region that is not under consideration

BOUNDARY: Demarcation between system and surrounding

MATTER: Anything at all, that has weight and occupies space

ENERGY: The ability to do work. Heat energy is usually implied in Chem. Eng

WORK: Product of the force applied and resulting distance moved

State of a System: The state of a system can be identified by property values (eg. pressure, temperature) required to reproduce the system.

Path of a System: Refers to the steps taken to reach certain property values

Simple Systems: Are devoid of any internal adiabatic, rigid, impermeable boundaries; no external force fields or internal forces. A simple system can be single or multi-phase.

Composite Systems: Are two or more simple systems

Open Systems: Allow matter, energy and work to pass across system boundary, either from surrounding to system or vice versa

Closed Systems: Allow only energy and work to pass across system boundary

Isolated Systems: Allow neither matter nor heat to pass across system boundary. No interactions with surroundings

Phase: Region of uniform properties (eg. a liquid phase has the same microscopic kinetic energy properties abi?)

Intensive Properties: Properties (or property values) of a system that do not depend on mass (eg. pressure, temperature-for instance, the boiling point of water does not increase when the quantity of water increases… the time will increase though). Intensive properties have zero order in mass

Extensive Properties: Properties of a system that depend on mass (eg. ) Extensive properties have 1st order in mass

Primitive Properties: Are measurable properties

Derived Properties: Are defined in terms of changes in the state of a system

Reversible Process: "A process will be called reversible if a second process could be performed in at least one way so that the system and all elements of its environment can be restored to their respective initial states, except for differential changes of second order”

Irreversible Process: When the system cannot be restored back to its initial state. All real or natural processes are irreversible, “hence reversible processes are only idealizations that are very useful in showing limiting behavior.”

Sign Conventions: This refers to the positive and negative signs assigned to work and energy, based on their directions; Heat transferred TO the system, as well as work done ON the system is assigned a POSITIVE sign. Vice versa for negative signs

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