热学物理SAT2热学课件

1、Heat and Thermodynamics Heat and Thermodynamics 1ReviewEnergy conservationMass conservation无外力做功，只存在动能和势能的转化反应前后质量不变Heat is the energy that is transferred between one object and another object because of a temperature difference that exists between them. 3Heat transferConductionConvectionRadiation接触

2、接触对流对流辐射辐射介质介质4Expansion （热胀冷缩）HotCoolLinear expansionVolume expansion线膨胀系数体积胀系数体积膨胀系数是线膨胀系数体积膨胀系数是线膨胀系数的的3倍倍56 Internal Energy (U) 将所有的能量都分为动能与势能 1.1.分子平均动能：物体内所有分子动能的平均值，分子平均动能：物体内所有分子动能的平均值，温度温度是其大小的标志。是其大小的标志。 2.2.分子势能：由分子间分子势能：由分子间相对位置相对位置决定的能量。决定的能量。改变物体的内能只有两种方法：改变物体的内能只有两种方法：Specific HeatWor

3、k done by ideal gas7Specific Heat 比热比热 )(ifTTcmTcmQ dTmdQc SI: J/kg.K.1kg1kg某物质每上升或下降某物质每上升或下降1 1所吸收或释放的能量所吸收或释放的能量Heat absorptionHeat release8Work on P-V DiagramReview求面积求面积positiveWnegativeWVVVPWonbygas theON done isWork gas theBY done is Work 9Internal Energy U of an Ideal GasKinetic theory of ga

4、ses 气体分子动理论气体分子动理论分子永不停息地做分子永不停息地做无规则运动无规则运动分子间存在着分子间存在着相互作用力相互作用力气体分子始终充满容器 (Diffusion)分子间存在势能0 PE理想气体无分子势能，理想气体无分子势能，只有动能只有动能气体分子碰撞过程中，气体分子碰撞过程中，能量损失忽略不计能量损失忽略不计气体分子气体分子体积忽略不计体积忽略不计10Ideal Gas lawBoyles LawCharles Law等温定律等温定律理想气体的能量Boltzmann constant11Law of ThermodynamicsLaw of Thermodynamics12Th

5、e First Law of Thermodynamics WQU UWQ 12UUU 能量守恒定律能量守恒定律JouleThe Second Law of Thermodynamics Kelvin热机效率热机效率热机效率不能等于热机效率不能等于100%13Four processesCase I: Isovolumetric process恒容过程恒容过程Case II: Isothermal Process恒温过程恒温过程Case III: Adiabatic process绝热过程绝热过程Case IV: Isobaric Process等压过程等压过程UWQ 做功与吸放热做功与吸放热

6、14Case I: Isovolumetric process恒容过程恒容过程V is constantW=pV=0UWQ U=QABTU0BATU0U=0Q = WBAVW0BAVW0U017Case IV: Isobaric Process等压过程等压过程UWQ P is constantW=pVAB VW0TQ0BAVW0 Q0U0CD：恒温可逆压缩：恒温可逆压缩W0U=0DA：绝热可逆压缩：绝热可逆压缩W0内能升高内能升高21冰箱原理冰箱原理Work input从低温到高温内能降低低温吸热，高温放热低温吸热，高温放热环境对系统做功环境对系统做功内能降低内能降低22THERMAL PRO

7、PERTIES OF MATTER23A 50 g cube of ice is added to 500 g of boiling water. Which of the following is most likely to occur?(A) The ice cube vaporizes before it strikes the bottom of the container.(B) The water boils more vigorously because the hot water draws cold from the ice cube.(C) The water in the container stops boiling during the phase change of the ice to water.(D) The more dense ice cube sinks in the less dense hot water.(E) Steam bubbles form on the