Set the syringe firmly on its base on the table and had someone click start. Wai

Question

Set the syringe firmly on its base on the table and had someone click start. Waited a second or two and then firmly and quickly pushed the syringe all the way down with hand. Held the syringe in this position until the both the temperature and pressure equalized and were no longer changing. Released the syringe and let it rise on its own. When the pressure and temperature again both stopped changing, clicked stop.....

a) What parts of the experiment are isochoric (or close to isochoric)? Which parts are distinctly non-isochoric? Explain with reference to graphs.......

b)What parts of the experiment are adiabatic (or close to adiabatic)? Which parts are distinctly non-adiabatic? Explain with reference to graphs

Explanation / Answer

An adiabatic process is any process occurring without gain or loss of heat within a system (i.e. during the process the system is thermodynamically isolated- there is no heat transfer with the surroundings). This is the opposite of a diabatic process, where there is heat transfer. A key concept in thermodynamics, many rapid chemical and physical processes are described or approximated in this way. Such processes are usually followed or preceded by events that do involve heat transfer (i.e. are non-adiabatic). Examples include electron-transfer. Adiabatic processes can occur if the container of the system has thermally-insulated walls or the process happens in an extremely short time, so that there is no opportunity for significant heat exchange.[1] Although the terms adiabatic and isocaloric can often be interchanged, adiabatic processes may be considered a subset of isocaloric processes; the remaining complement subset of isocaloric processes being processes where net heat transfer does not diverge regionally such as in an idealized case with mediums of infinite thermal conductivity or non-existent thermal capacity. For example, an adiabatic boundary is a boundary that is impermeable to heat transfer and the system is said to be adiabatically (or thermally) insulated; an insulated wall approximates an adiabatic boundary. Another example is the adiabatic flame temperature, which is the temperature that would be achieved by a flame in the absence of heat loss to the surroundings. An adiabatic process may be described by the statement where is the energy transferred by heating (or cooling). Since, by the second law of thermodynamics, for a reversible process (where T is temperature and S is entropy), a reversible adiabatic process is also an isentropic process (). However, for an irreversible process, so that an irreversible adiabatic process is not isentropic. In particular, an adiabatic process that is irreversible and extracts no work (e.g. viscous drag) is in an isenthalpic process, in which entropy increases. One opposite extreme—allowing heat transfer with the surroundings, causing the temperature to remain constant—is known as an isothermal process. Since temperature is thermodynamically conjugate to entropy, the isothermal process is conjugate to the isentropic process, and therefore to a reversible adiabatic process. A transformation of a thermodynamic system can be considered adiabatic when it is quick enough that no significant heat is transferred between the system and the outside. At the opposite extreme, a transformation of a thermodynamic system can be considered isothermal if it is slow enough so that the system's temperature remains constant by heat exchange with the outside. The term "adiabatic" literally means impassable,[2] coming from the Greek roots ?- ("not"), d??- ("through"), and ßa??e?? ("to pass"); this etymology corresponds here to an absence of heat transfer. Contents [hide] 1 Adiabatic heating and cooling 2 Ideal gas (reversible process) 2.1 Example of adiabatic compression 2.2 Adiabatic free expansion of a gas 2.3 Derivation of continuous formula for adiabatic heating and cooling 2.4 Derivation of discrete formula 3 Graphing adiabats 4 See also 5 References 6 External links [edit]Adiabatic heating and cooling Adiabatic changes in temperature occur due to changes in pressure of a gas while not adding or subtracting any heat. In contrast, free expansion is an isothermal process for an ideal gas. Adiabatic heating occurs when the pressure of a gas is increased from work done on it by its surroundings, e.g. a piston. Diesel engines rely on adiabatic heating during their compression stroke to elevate the temperature sufficiently to ignite the fuel. Adiabatic heating also occurs in the Earth's atmosphere when an air mass descends, for example, in a katabatic wind or Foehn or chinook wind flowing downhill over a mountain range. When a parcel of air descends, the pressure on the parcel increases. Due to this increase in pressure, the parcel's volume decreases and its temperature increases, thus increasing the internal energy. Adiabatic cooling occurs when the pressure of a substance is decreased as it does work on its surroundings. Adiabatic cooling occurs in the Earth's atmosphere with orographic lifting and lee waves, and this can form pileus or lenticular clouds if the air is cooled below the dew point. When the pressure applied on a parcel of air decreases, the air in the parcel is allowed to expand; as the volume increases, the temperature falls and internal energy decreases. Adiabatic cooling does not have to involve a fluid. One technique used to reach very low temperatures (thousandths and even millionths of a degree above absolute zero) is adiabatic demagnetisation, where the change in magnetic field on a magnetic material is used to provide adiabatic cooling. Also, the contents of an expanding universe (to first order) can be described as an adiabatically cooling fluid. (See - Heat death of the universe) Rising magma also undergoes adiabatic cooling before eruption, particularly significant in the case of magmas that rise quickly from great depths such as kimberlites.[3] Such temperature changes can be quantified using the ideal gas law, or the hydrostatic equation for atmospheric processes. No process is truly adiabatic. Many processes are close to adiabatic and can be easily approximated by using an adiabatic assumption, but there is always some heat loss; as no perfect insulators exist. [edit]Ideal gas (reversible process) Main article: Reversible adiabatic process For a simple substance, during an adiabatic process in which the volume increases, the internal energy of the working substance must decrease The mathematical equation for an ideal gas undergoing a reversible (i.e., no entropy generation) adiabatic process is where P is pressure, V is volume, and being the specific heat for constant pressure, being the specific heat for constant volume, is the adiabatic index, and is the number of degrees of freedom (3 for monatomic gas, 5 for diatomic gas). For a monatomic ideal gas, , and for a diatomic gas (such as nitrogen and oxygen, the main components of air) .[4] Note that the above formula is only applicable to classical ideal gases and not Bose–Einstein or Fermi gases. For reversible adiabatic processes, it is also true that where T is an absolute temperature. This can also be written as [edit]Example of adiabatic compression Let's now look at a common example of adiabatic compression- the compression stroke in a gasoline engine. We will make a few simplifying assumptions: that the uncompressed volume of the cylinder is 1000cc's (one liter), that the gas within is nearly pure nitrogen (thus a diatomic gas with five degrees of freedom and so = 7/5), and that the compression ratio of the engine is 10:1 (that is, the 1000 cc volume of uncompressed gas will compress down to 100 cc when the piston goes from bottom to top). The uncompressed gas is at approximately room temperature and pressure (a warm room temperature of ~27 degC or 300 K, and a pressure of 1 bar ~ 100,000 Pa, or about 14.7 PSI, or typical sea-level atmospheric pressure). so our adiabatic constant for this experiment is about 1.58 billion. The gas is now compressed to a 100cc volume (we will assume this happens quickly enough that no heat can enter or leave the gas). The new volume is 100 ccs, but the constant for this experiment is still 1.58 billion: so solving for P:

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