What do Cp and Cv signify?

An important point right in the beginning is solids and liquids because of their tight molecular network, can't perform thermodynamic work PV. Their total energy is their internal energy. But in the case of gases, they can expand when heated and therefore they consume a part of the total energy which is Cp known as Cv while expansion. Therefore, gases have two specific heats, Cp and Cv. While solids and liquids have just a specific heat.

Specific heat constant pressure: Cp

Cp is the amount of heat energy released or absorbed by the unit mass of the substance with the change in temperature at constant pressure. In other words, it is the heat energy transfer at a constant pressure between a system and its surroundings.

Specific heat constant volume: Cv

During a small change in the temperature of a substance, Cv is the amount of heat energy released or absorbed by the unit mass of the substance with the change in temperature at constant volume. In other words, it is the heat energy transfer between a system and surroundings when there is no change in volume.

What is the meaning of this?

Cp:

When heat is transferred at a constant pressure with volume increasing, in a typical case with gas, the gas expands. To create space for expansion the gas has to do mechanical work to push the surrounding. This is additional energy required by the gas compared to a situation where there is no expansion of gas and the energy gets spent only to increase the kinetic energy of gas molecules. :

Cv

At constant volume, since there is no expansion, there is no work, heat just goes to increase the kinetic energy of molecules.?For gases, Cp> Cv. Because Cp signifies total energy and Cv represents a part of total energy which is internal energy.

Cp represents the change in total energy (H) concerning temperature (T) at constant pressure and is given by Cp = dH / T. On the other hand, Cv represents the change in internal energy (U) concerning temperature at constant volume and is given by Cv = dU / dT.Cp-Cv = RT

The difference between Cp and Cv denoted as Cp - Cv, represents the work done (PdV) by an ideal gas at constant pressure. This relation comes from the first law of thermodynamics equation, H = U + PV, at constant pressure.Cp/Cv = y = Adiabatic index

The ratio Cp / Cv signifies the internal energy available in an adiabatic process as a proportion to the total energy CpT at constant pressure. This ratio is also known as the adiabatic index for an ideal gas, and it is a measure of the amount by which the pressure and density of a gas vary in an adiabatic process. For diatomic gases, the adiabatic index is typically 1.4, meaning the internal energy available in an adiabatic process is 1.4 times the total energy Cp T at constant pressure.

Thus, it can also be said that the heat capacity ratio is the ratio between the enthalpy to the internal energy: y = Cp/Cv = H/U [ Enthalpy divided by internal energy]