This model illustrates the isochoric processes in a gas. An isochoric process is a process of quasi-static heating or cooling of a given substance with a constant volume V. The state of the gas is presented on the P-T and V-T diagrams. An isochoric process that occurs in an ideal gas can be represented using the (P,T) diagram through a set of straight lines P~T that are determined by the different gas volumes. For one mole of an ideal gas,
= const =
, where R = 8.31 J/(mole K) is the universal gas constant. In an isochoric process, mechanical work is not produced: W = 0 The first law of thermodynamics implies that Q = U(T2) - U(T1) = ΔU, where U(T1) and U(T2) are the internal energies of the gas in the initial and final states. During the isochoric heating of a gas, the gas absorbs a certain amount of heat, and its internal energy increases. During the isochoric cooling of a gas, the internal energy of the gas decreases as it transfers some of its internal energy to the adjacent physical bodies. Modify the gas volume, and observe the result that the modification has on the isochoric process. Study the dependency graph p(T) of an isochoric process on your computer screen. Observe the quantity of heat Q that is obtained by the gas, the amount work W done by the gas, and the change ΔU in the gas' internal energy via the energy diagram. Note that in an isochoric process the work performed by the gas equals zero. The entirety of the absorbed heat goes to change the internal energy of the gas.