# Physical Science Physics Course - Topic X - RANDOM

Discussion in 'Physical Science' started by Icewolf, Mar 31, 2005.

Laws of Thermodynamics

In our Universe we find that energy exists in many forms, e.g light, heat, chemical and nuclear etc. Energy describes the ability to influence the Universe and bring about change or to do work.
(AKA work done covered later in the energy topic)

First Law of Thermodynamics

Energy cannot be created or destroyed it can only be changed from one form to another, Therefore the total amount of energy and matter in the Universe remains constant, merely changing from one form to another. The First Law of Thermodynamics (Conservation) states that energy is always conserved, it cannot be created or destroyed. In essence, energy can be converted from one form into another.

The Second Law of Thermodynamics (entropy)

"in all energy exchanges, if no energy enters or leaves the system, the potential energy of the state will always be less than that of the initial state." This is also commonly referred to as entropy. A machine i.e a wound up toy will run until the potential energy in the spring is converted, and not again until energy is reapplied to the spring to rewind it; the organism will get no more until energy is input again. In the process of energy transfer, some energy will dissipate as heat. Entropy is a measure of disorder: cells are NOT disordered and so have low entropy. The flow of energy maintains order and life. Entropy wins when organisms cease to take in energy and die.

2. ### Derek■֎؜♫■Staff Member

*UPDATE*

Zeroth Law of Thermodynamics

The zeroth law of thermodynamics is a generalized statement about bodies in contact at thermal equilibrium and is the basis for the concept of temperature. The most common enunciation of the zeroth law of thermodynamics is: â€œIf two thermodynamic systems are in thermal equilibrium with a third, they are also in thermal equilibrium with each other.â€

In order words, the zeroth law says that if considered a mathematical binary relation, thermal equilibrium is transitive.

A system in thermal equilibrium is a system whose properties (like pressure, temperature, volume, etc.) are not changing in time. A hot cup of coffee sitting on a kitchen table is not at equilibrium with its surroundings because it is cooling off and decreasing in temperature. Once its temperature stops decreasing, it will be at room temperature, and it will be in thermal equilibrium with its surroundings.

Two systems are said to be in thermal equilibrium when 1) both of the systems are in a state of equilibrium, and 2) they remain so when they are brought into contact, where 'contact' is meant to imply the possibility of exchanging heat, but not work or particles. And more generally, two systems can be in thermal equilibrium without thermal contact if one can be certain that if they were thermally connected, their properties would not change in time.

Thus, thermal equilibrium is a relation between thermodynamical systems. Mathematically, the zeroth law expresses that this relation is an equivalence relation. (Technically, we would need to also include the condition that a system is in thermal equilibrium with itself.)

Third Law of thermodynamics

The third law of thermodynamics is an axiom of nature regarding entropy and the impossibility of reaching absolute zero of temperature. The most common enunciation of third law of thermodynamics is: â€œAs a system approaches absolute zero of temperature all processes cease and the entropy of the system approaches a minimum value."

In simple terms, the Third Law states that the entropy of a pure substance approaches zero as the absolute temperature approaches zero. This law provides an absolute reference point for the determination of entropy. The entropy determined relative to this point is the absolute entropy.

There still seems to be considerable debate over laws beyond the 4 accepted by scientists as the basic laws of science, mostly dealing with environmental sciences, biological evolution, and galactic phenomena.

I love Wikipedia

3. ### Mark♤♡◇♧Staff Member

This thread compiled and attributed to the esteemed author from the forums, as a perfect example of a well constructed article, with additional attribution of the images supplied by tablet.

Thank you Ice !!