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Level 140

Thermodynamics


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Thermodynamics
physics that is concerned with energy, transfers and work.
Statistical Thermodynamics
The interpretation of the laws of thermodynamics in terms of the average behavior of the large numbers of atoms and molecules that make up a typical sample.
Heat and Work
Two fundamental concepts of thermodynamics; two ways in which energy can be transferred.
system
A collection of components organized to accomplish a specific function or set of functions.
universe
All of the known or supposed objects and phenomena throughout space.
Open System
A system in which both energy and matter can enter or exit
Closed System
A system containing a fixed amount of matter; it can still exchange energy with the surroundings.
Isolated System
A system that has are no energy transfers between that system and its surroundings.
7.1 Systems Summary
In thermodynamics, the universe consists of a system and its surroundings. An open system can exchange both matter and energy with the surroundings; a closed system can exchange only energy; an isolated system can exchange nothing.
work
a force acting upon an object to cause a displacement. (key words: force, displacement, and cause)
Calculating the work to move an object
The work required to move an object a certain distance against an opposing force is calculated by multiplying the opposing force by the distance moved against it:
Energy
(physics) the capacity of a physical system to do work
u
average speed of a molecule
∆X
A symbol; ∆X means a change in the property X.
Work on/by a system
Work done on a system increases its internal energy.
w
angular speed
7.2 Work and Energy Summary
Work is the transfer of energy to a system by a process that is equivalent to raising or lowering a weight. For work done on a system, w is positive, for work done …
Expansion work
Types of Work
Nonexpansion Work
Work that does not involve a change in volume of a system, ex. a battery.
pressure = force × area
How the work done when a system expands through a volume V is related to the external pressure P₋ex
w = -P₋ex ∆V
Work done when a system expands by ∆V against constant external pressure P₋ex
If P₋ex is zero
If P₋ex = 0, i.e. it is a vacuum, then w = 0.