Basic thermodynamics - Wikiversity
Early scientists explored the relationships among the pressure of a gas (P) and its temperature (T), volume (V), and amount (n) by holding two of the four. Consequently, their relatively small volume is insignificant and does not interfere with the relationships of pressure, volume, and temperature. Temperature; Pressure; Volume the relationship between thermodynamic temperature (T), pressure (P) and volume (V) of gases.
Equations of State Problems The majority of process operations involve material that is in a gaseous state. These conditions are not isolated extremes, but rather conditions that are typically encountered in various hydrocarbon processing units. Given this wide range of operating conditions, it is critical that a process technologist understand the behavior of gases under extreme conditions.
However, as just noted, many processes are carried out under conditions that are anything but normal. In general, the molecules, or atoms in the cases of the inert gases, are widely spaced. Consequently, their relatively small volume is insignificant and does not interfere with the relationships of pressure, volume, and temperature that we refer to as PVT. But under the extreme conditions of high pressure and low temperature just described, that molecular volume does interfere and causes a gas to behave in a nonideal manner that results in a larger volume.
Relationships among Pressure, Temperature, Volume, and Amount
The Temperature-Volume Law This law states that the volume of a given amount of gas held at constant pressure is directly proportional to the Kelvin temperature. V Same as before, a constant can be put in: Also same as before, initial and final volumes and temperatures under constant pressure can be calculated. The Pressure Temperature Law This law states that the pressure of a given amount of gas held at constant volume is directly proportional to the Kelvin temperature.
P Same as before, a constant can be put in: The Volume Amount Law Amedeo Avogadro Gives the relationship between volume and amount when pressure and temperature are held constant. Remember amount is measured in moles. Also, since volume is one of the variables, that means the container holding the gas is flexible in some way and can expand or contract.
If the amount of gas in a container is increased, the volume increases.
If the amount of gas in a container is decreased, the volume decreases. V As before, a constant can be put in: The Combined Gas Law Now we can combine everything we have into one proportion: The volume of a given amount of gas is proportional to the ratio of its Kelvin temperature and its pressure. One might say 'that fire has a lot of heat in it'.
In physics however, the word heat has a very distinct meaning. Heat is a form of energy which is held in matter by the constant jostling of its particles. In macroscopic thermodynamics, heat can be thought of as a massless, invisible substance that can flow from one region to another, but it is very important to remember that this is NOT a real or accurate description of heat, merely a tool to help you visualise how matter and the energy contained within it behaves in the 'real world' as we see it.
In reality, heat is an effect of the movement of particles - whether they be atomsionsmoleculeselectronsphotons or any kind of fictional 'magic' particle you could care to imagine.
Gas Laws: Pressure, Volume, and Temperature
Particles transfer heat between one another by colliding with one another, and over time this will cause heat to flow around in large bodies of matter where it allowed to. Heat is represented in a formula by the symbol Q, and its unitslike other forms of energyare Joules, which have the symbol J Example: Thermodynamic variables[ edit ] Thermodynamic variables are those properties of a real system which can be observed by simple apparatus on a scale that can be readily understood by human beings.
These contrast with statistical variables which by and large are estimations and inferred quantities relevant to the atoms within a material, whose existence is not relevant to macroscopic thermodynamics.