Jumat, 11 Mei 2012

THERMODYNAMIC PHYSICS

A system undergoes a thermodynamic process when there is some sort of energetic change within the system, generally associated with changes in pressure, volume, internal energy (i.e. temperature), or any sort of heat transfer.
There are several specific types of thermodynamic processes that have special properties:

Heat Capacity:

The heat capacity, C, of an object is the ratio of change in heat (energy change - denoted by delta-Q) to change in temperature (delta-T).
C = delta-Q / delta-T
The heat capacity of a substance indicates the ease with which a substance heats up. A good thermal conductor would have a low heat capacity, indicating that a small amount of energy causes a large temperature change. A good thermal insulator would have a large heat capacity, indicating that much energy transfer is needed for a temperature change.

Ideal Gas Equations:

There are various ideal gas equations which relate temperature (T1), pressure (P1), and volume (V1). These values after a thermodynamic change is indicated by (T2), (P2), and (V2). For a given amount of a substance, n (measured in moles), the following relationships hold:
Boyle's Law (T is constant):
P1V1 = P2V2 Charles/Gay-Lussac Law (P is constant):
V1/T1 = V2/T2
Ideal Gas Law:
P1V1/T1 = P2V2/T2 = nR
R is the ideal gas constant, R = 8.3145 J/mol*K. For a given amount of matter, therefore, nR is constant, which gives the Ideal Gas Law.

Laws of Thermodynamics:

• Zeroeth Law of Thermodynamics - Two systems each in thermal equilibrium with a third system are in thermal equilibrium to each other.
• First Law of Thermodynamics - The change in the energy of a system is the amount of energy added to the system minus the energy spent doing work.
• Second Law of Thermodynamics - It is impossible for a process to have as its sole result the transfer of heat from a cooler body to a hotter one.
• Third Law of Thermodynamics - It is impossible to reduce any system to absolute zero in a finite series of operations. This means that a perfectly efficient heat engine cannot be created.

The Second Law & Entropy:

The Second Law of Thermodynamics can be restated to talk about entropy, which is a quantitative measurement of the disorder in a system. The change in heat divided by the absolute temperature is the entropy change of the process. Defined this way, the Second Law can be restated as:
In any closed system, the entropy of the system will either remain constant or increase.
By "closed system" it means that every part of the process is included when calculating the entropy of the system.