1, the specific heat capacity of steam is greater than that of water. If water vapor is mixed into the air, the specific heat capacity of the gas measured by the experimental results will be larger than the actual one.
2. If the period of the vibrating object is long, the original formula is not applicable. Because the vibration period of the object is too long, it means that the vibration without problems is too slow, and the vibration of the object is too slow to be regarded as an adiabatic process, and the adiabatic equation is not applicable. Vibration that is too slow cannot be regarded as simple harmonic vibration. The applicable condition of this formula is that the object is in simple harmonic vibration during adiabatic process.
Extended data
Calculation method of specific heat capacity of gas;
A physical quantity that describes the characteristics of system temperature change when gas exchanges heat with the outside world. To calculate the specific heat capacity of an ideal gas system composed of n molecules of the same kind, the partition function q of molecules in Boltzmann statistics is usually obtained first. Then, under the condition that the internal energy volume v in the system is constant, the constant volume molar heat capacity can be obtained by taking the derivative of the temperature t. If n in the formula is replaced by avogadro number, the constant volume molar heat capacity can be obtained, which is also called constant volume molar heat capacity.
For an ideal gas, the constant pressure heat capacity CP0 can be obtained according to the thermodynamic formula. Molecules are composed of atoms, and atoms are composed of nuclei and extranuclear electrons. The molecular energy level εi of the partition function should contain these components. Because of the energy difference between states with different spin orientations, the nucleus is an ultra-fine structure in the generation of atomic spectrum, and the interaction between nuclear spin and electron shell is very weak, so its influence can generally be ignored in the thermodynamic process.
Because the difference between the lowest energy level and the nearest sub-high energy level is much larger than nT, it is difficult to excite electrons. When the temperature changes, it is still in the ground state and does not contribute to the heat capacity. Without considering the atoms with nuclear decay, εi in the partition function formula has only three parts of energy: the whole mass center translation, the whole rotation and the relative vibration between internal atoms.
1, translation section. The relative distance between translational energy levels can be ignored, and the thermal motion of molecules can always be regarded as continuous, so the contribution of translational parts to heat capacity can be treated by the energy equipartition theorem. The contribution of the degree of freedom of molecular translation to the constant volume heat capacity is, while the constant volume molar heat capacity is (hereinafter referred to as the specified volume molar heat capacity), and r is the molar gas constant.
2. Rotating part. The heavier or more atoms make up polyatomic molecules, the greater the moment of inertia, and the less visible the quantum effect of rotation. Generally, only the quantum properties of light diatomic molecular gas rotation at low temperature are considered; Other polyatomic molecules or diatomic molecules containing heavy atoms can generally be treated classically.
3. Vibration part. The vibration energy level spacing of most polyatomic molecules at room temperature is much larger than the thermal motion energy kT, so it is not easy to excite them to participate in thermal motion, so they do not contribute to the specific heat capacity. Only at high temperature can we make a contribution; When the temperature is high, it can be treated classically. In fact, it is almost impossible for gas molecules composed of more than two atoms to reach the temperature of classical treatment, because polyatomic molecules have already decomposed.
Baidu encyclopedia-gas specific heat capacity