The Laws of Thermodynamics
Thermodynamics is the relationship between kinetic and potential energy and heat. (CA)
The science of the relations between heat and other (mechanical, electrical, etc.) forms of energy (OX)
System = a complex whole; a set of connected things or parts; an organized body of material or immaterial things (OX)
The system is surrounded by the rest of the universe (surroundings) – we make our scientific observations from outside the system (in theory)
DG Understand that observing the system or process might alter the operation of the system or process. In addition you must understand your viewpoint to better understand what you are learning.
Open system = matter added or removed a boiling pot, heat must be added to keep it boiling
Closed system = impervious boundary the earth acts like a closed system
Temperature is a measure of the heat energy in a body (system).
(OX) the degree or intensity of heat of a body, air mass, etc., in relation to others
Heat added to a body causes an increase in molecular motion, more heat equals more motion.
Heat energy “happens” at the molecular level.
“…as the temperature is raised means that more molecules are moving (including rotating and vibrating) more vigorously, or that atoms trapped at their locations in solids are vibrating more vigorously about their average positions. Turmoil and temperature go hand in hand.” P. 15
We pretend (visualze) that heat flows.
“In everyday language, heat is both a noun and a verb. Heat flows, we heat. In thermodynamics heat is not an entity or even a form of energy: heat is a mode of transfer of energy. It is not a form of energy, or a fluid of some kind, or anything of any kind. Heat is the transfer of energy by virtue of a temperature difference. Heat is the name of a process, not the name of an entity.” P. 22
“heat is the transfer of energy that makes use of the random motion of atoms in the surrounding.” P. 25
Work is motion against an opposing force.
All work is equivalent to the raising of a weight.
The capacity of a system to do work is called energy
Perpetual motion = work produced without consumption of a fuel. (NOT POSSIBLE)
“Work is energy tamed, and requires greater sophistication to contrive.” (fire is easy, making a nuclear plant is really difficult)
Enthalpy = total energy of something, water vapor contains the latent heat of vaporization (SH)
First Law
Conservation of energy
In a closed system the total amount of energy, including heat is conserved.
Energy cannot be created
Energy cannot be destroyed
Energy can “move” or convert from one form to another.
The universe is a closed system!
The second law
“… not knowing the second law of thermodynamics is the equivalent to never having read Shakespeare. 37
There will always be waste and disorder, the question is, how much?
Heat will not flow from cold to hot!
Heat flows only from hot to cold!
Refrigeration requires moving heat and this requires work.
Fast moving hot particles collide with cold slow moving particles and some energy transfers from the hot to the cold. The fast particles slow down the slow ones speed up.
Heat energy moves from concentrated and organized to diffused and disorganized.
No machine or process can be 100% efficient – ever!
“No matter how generously lubricated and engine may be, no matter how beautifully honed and fitted its gears, some amount of the energy that drives it will be lost as heat, will be puffed into the sky rather than turned to the task at hand.”
Cells and plants are not very efficient.
Every isolated system grows more disordered over time.
Entropy = how much energy in a system that is not available to do work.
Energy can be concentrated through the doing of work, but when that energy is used it will dissipate and become unusable for the doing of work.
“By the second law of thermodynamics, the energy of a system may remain the same in quantity, while steadily declining in quality. The concentrated energy of petroleum is quite useful; the dispersed energy of excited molecules of carbon dioxide and nitrogen oxide belched out of a car’s exhaust is not.”
ENTROPY
“low entropy means high quality ORGANIZED
high entropy means low quality DISORGANIZED.” 38
Heat engine “consists of a piston or turbine – for converting heat into work, and a cold sink, a place for discarding any unused energy as heat.” 39 the cold sink is often just the atmosphere
“In other words, Nature exerts a tax on the conversion of heat into work, some of the energy supplied by the hot source must be paid into the surroundings as heat.”
Spontanious change = occurs naturally high energy (hot) to low energy (cold), non spontaneous requires work low energy to high energy
“The steam engine, in its abstract form as a device that generates organized motion (work) by drawing on the dissipation of energy, accounts for all the process within our body. Moreover that great steam engine in the sky, the Sun, is one of the great fountains of energy. We all live of the spontaneous dissipation of its energy, and as we live so we spread disorder into our surrounds: we could not survive without our surroundings.” 62
John Donne (1572-1631).
“No man is an island, entire of itself...any man’s death diminishes me, because I am involved in mankind; and therefore never send to know for whom the bell tolls; it tolls for thee.”
We live on a planetary island
Third law = It is impossible to attain absolute zero -273° C
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