ΔE＝qm-cmΔt
(1) When water freezes under standard conditions, the kinetic energy of water does not change. The potential energy of water will decrease;
(2) Under normal circumstances, during the heating process of an object, both the kinetic energy and potential energy of the object increase;
(3) This question is A special process of exothermic heating. In the problem, the decrease in the potential energy of the object is greater than the increase in the kinetic energy of the object.
Molecular kinetic energy and molecular potential energy are two inseparable parts of the internal energy of an object, and molecular kinetic energy and molecular potential energy have their own determining factors. In the process of analyzing and calculating problems, we must deal with molecular kinetic energy and molecular potential. Potential energy, conduct separate analysis and calculation.
[Idea 1] According to the concepts of molecular potential energy and molecular kinetic energy, the change of molecular potential energy is determined by the average distance between molecules and the total number of molecules. In this question, the heat of fusion released during the process and the heating process should be used. The specific heat absorbed can be solved by the concepts of fusion heat and specific heat; and the change of molecular kinetic energy is determined by the total number of molecules and temperature, so this problem should be solved by specific heat.
[Idea 2] According to the second law of thermodynamics, considering that the work done in the process of doing work can be ignored, and the heat released during the heat transfer process is the main contradiction of the problem, then use the conversion of energy and The energy conversion relationship in the conservation law analysis process, and the equations are solved.
[Three ideas] According to the law of energy conversion and conservation, analyze the energy conversion relationship in the process and list the equations. Based on the heat of fusion released during the process and the specific heat absorbed during the heating process, the corresponding equations are listed for solution.
★ Detailed explanation of the test question: (Based on idea 1)
The process of liquid solidification is the process of reducing the total potential energy of molecules. The reduction should be qm, while the process of temperature increase is It is the process in which the average kinetic energy of molecules increases, that is, the total kinetic energy of molecules increases. The increase in the total kinetic energy of the molecules should be cmΔt. Since the whole is exothermic, the internal energy should decrease, and the decrease should be equal to the decrease in the total potential energy of the molecules of the object minus the molecules. The increase in total kinetic energy.
That is, ΔE=qm-cmΔt
This question is about the change of the internal energy of the object, and the internal energy of the object is determined by the total kinetic energy of the object's molecules and the total potential energy of the object's molecules. Although potential energy and kinetic energy can be converted into each other, there is no direct correspondence and should be analyzed and calculated separately.