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热力学第一定律是包括内能在内的能的转化和守恒定律。其数学表达式为: W+Q=△E为了帮助学生加深理解热力学第一定律的内容和培养学生归纳知识的能力,在教学中要注意适时地将新旧知识进行综合归纳。例如在讲到由于热传递而使物体内能发生变化时,可以联系物态变化过程中物体内能的改变及其量度。可列表如下(见图1): 上表(图1)中物体处于固态、液态、气态时,由于热传递使它们温度升高、体积膨胀,内能发生了变化。内能改变量,分别用公式Q=C_固m△t、Q=C_液m△t、Q=C_气m△t进行量度,其中应注意指出的是:对气体来讲有定容比热和定压比热,气体的定压比热总大于它的定容比热。由于升温体积膨胀,对固体、液体和气体的体积变化与温度变化的关系如下: 固态:V_t=V_0(1+β_固△t); 液态:V_t=V_0(1+β_液△t); 气态:P△V=M/μR△T。公式P△V=M/μR△T说明当气体的P、M、μ一定时,△V随△T的变化关系。可以引导学生进行推导:
The first law of thermodynamics is the transformation and conservation of energy including internal energy. The mathematical expression is: W + Q = △ E In order to help students deepen the understanding of the contents of the first law of thermodynamics and the ability to develop students’ inductive knowledge, we must pay attention to the timely synthesis of old and new knowledge. For example, when the change of the internal energy of an object due to heat transfer is mentioned, the change of the internal energy of the object during the change of state of the object and its measurement can be connected. Can be listed as follows (see Figure 1): In the above table (Figure 1) objects in the solid, liquid, gas, due to heat transfer so that their temperature increases, volume expansion, internal energy has changed. The internal energy can be changed by the formula Q=C_solid mΔt, Q=C_liquid mΔt, and Q=C_gas m△t, respectively. It should be noted that the gas is determined Specific heat ratio and constant pressure specific heat, the constant pressure specific heat of the gas is always greater than its constant specific heat. Due to volume expansion, the relationship between volume change and temperature change of solids, liquids, and gases is as follows: Solid state: V_t=V_0 (1+β_solid Δt); Liquid state: V_t=V_0 (1+β_liquid Δt) Gaseous: PΔV=M/μR△T. The formula PΔV=M/μR△T shows that when the P, M, and μ of the gas are constant, the ΔV changes with ΔT. Can guide students to derivation: