Chapter 1: Intro Concepts and Definitions Flashcards
System
The object of study; The composition of the matter in the system may be fixed or may change through chemical or nuclear reactions. The shape or volume doesn’t have to be constant.
Surroundings
Everything external to the system.
Boundary
The separation between a system and its surroundings.
Closed Systems (Control Mass)
Fixed quantity of matter within a system. There is no transfer of mass across its boundary.
Control Volume (Open System)
Is a region of space (boundary) through which mass may flow in and out.
Control Surface (Boundary)
When the term control mass and control volume are used, the system boundary is often referred to as a control surface.
Isolated System
a closed system that doesn’t interact with its surroundings in any way.
Choosing a system boundary take into consideration…
- what is known about possible system, particularly at boundaries.
- objective for analysis.
property
is a macroscopic character of a system such as mass, volume, energy, pressure and temperature to which a numerical value can be assigned at a given time without knowledge of the previous behavior.
State
Condition of a system as described by its properties.
Process
a transformation from one state to another.
Steady State
when the properties of a system don’t change over time.
Extensive Properties
properties that depend on the size/ extent of the system. Functions of only time. Ex: Mass, Volume, Energy.
Intensive Properties
properties that are independent of the size or extent of a system at any moment. Are functions of bot position and time. Ex: Specific Volume, Temperature
Determining what is a Property
A quantity is a property if, and only if , its change in value between two states id independent of the process. ( only depends on end states not process path)
Equilibrium
In mechanics, equilibrium means a condition of balance maintained by an equality
of opposing forces. In thermodynamics, the concept is more far-reaching, including
not only a balance of forces but also a balance of other influences.
Equilibrium State
Isolate the system from its surroundings and
watch for changes in its observable properties.If there are no changes, we conclude
that the system was in equilibrium at the moment it was isolated.
Specific Volume
The specific volume y is defined as the reciprocal of the density. It is the volume per unit mass. Like density, specific volume is an intensive property
and may vary from point to point.
Zeroth Law of Termodynamics
It is a matter of experience that when two objects are in thermal equilibrium with a third object, they are in thermal equilibrium with one another.
Ex: It is necessary only to see if they are individually in thermal equilibrium with a third object. The third object is usually a thermometer .
