物质的热行为90.pptVIP

17. Thermal Behavior of Matter 物質的熱行為 Gases 氣體 Phase Changes 相變 Thermal Expansion 熱膨脹 What unusual property of water is evident in this photo? 這照片顯露了水的那一種特性？ Ice is less dense than water. 冰的密度比水低。 17.1. Gases 氣體 The Ideal Gas Law: 理想氣體定律： A piston-cylinder system. 一個活塞-氣缸系统。 k = 1.38?10?23 J / K = Boltzmann’s constant 波爾茲曼常數 N = number of molecules 分子數目 NA = 6.022?1023 = Avogadro’s number 阿佛加德羅數字 = number of atoms in 12 g of 12C 12克12C裏面的原子數 n = number of moles (mol) 摩爾數 1 mole of matter contains NA molecules. 一摩爾包含 NA 個分子 = 8.314 J / K mol = Universal gas constant 通用氣體常數 All gases become ideal if sufficiently dilute. 在充份稀釋後，所有氣體都會變成理想。 Example 17.1. STP 標準温壓 What volume is occupied by 1.00 mol of an ideal gas at standard temperature pressure (STP), where T = 0?C, p = 101.3 kPa = 1 atm? 在標準温壓下 ( T = 0?C, p = 101.3 kPa = 1 atm )， 1.00 mol 理想氣體的體積為何？ ( last figure subject to round-off error ) 末位數含四捨五入誤差 Kinetic Theory of the Ideal Gas 理想氣體的運動理論 Kinetic theory 運動理論 ( Newtonian mechanics 牛頓力學 ): Gas consists of identical “point” molecules of mass m. 氣體由全部一樣，質量為 m 的〝點〞分子組成。 No interaction between molecules, except when they collide. 分子之間除碰撞時無相互作用。 Random motion. 隨機運動。 Collisions with wall are elastic. 與容壁的碰撞都是彈性的。 表面積 Molecule i collides with right-hand wall (RHW). 分子 i 碰上右壁 Momentum transfer to wall is 動量轉移為 No intermolecular collision Next collision with RHW occurs at 無分子互撞 ?下次碰撞右壁的時間為 Average force of i on RHW: i 加於右壁的平均力為 Random motion ? 隨機運動 ? Ideal gas law is recovered if 欲得理想氣體定律，祗需 T ~ ?K? in out Example 17.2. Air Molecule 空氣分子 Find ?K? of a molecule in air at room temperature ( 20?C = 293K), 找出在室温 (20?C = 293K) 空氣中一個分子的 ?K? ， determine the speed of a N2 molecule with this energy. 再决定一個能量為此值的氮分子(N2)的速率。 Thermal speed: 熱速率 Distribution of Molecular Speeds 分子速率的分佈 Maxwell-Boltzmann Distribution: (elastic collisions between free particles) 麥克斯韋-波爾茲曼分佈: ( 自