4 Transformasi Fasa Zat Murni_Masykuri 2018.pptx

pendidikan fisika

1. Transformasi Fasa Zat Murni Dr. M. Masykuri, M.Si. Chemistry Education Study Program Teacher Training and Education Studies Sebelas Maret Universit y ( UNS ) Website: http://masykuri.staf.fkip.uns.ac.id, email: [email protected] Solo, M ei 201 8 Transformasi Energi

2. Phase & Phase Transition Phase – suatu bentuk materi yang seragam pada semua bagian secara fisika dan kimia (a form of matter that is uniform throughout in chemical composition and physical state (J. Willard Gibbs )) Ice, - water, air, - NaCl solution Dua fasa berbeda saling dibatasi oleh 1/lebih Batas fasa (Boundaries, wall)

3. Phase & Phase Transition Phase - Suatu zat dapat membentuk 2 fasa karbon murni dapat membentuk alotropi: Grafit Diamond Grafit Diamond

4. Phase & Phase Transition Phase - Dua zat/lebih dapat membentuk 1 fasa. Lelehan Pt dan Au Campuran gas

5. Phase & Phase Transition Phase Diagram : is a P,T plot showing regions of thermodynamically stable phases Lines separating phases are called phase boundaries Vapor-liquid boundary shows variation of vapor pressure with temperature Solid-liquid boundary shows variation of sublimation pressure with temperature

6. µ a = µ b Penurunan Potensial Kimia Dalam batas-batas fasa, berlaku: µ a (p,T) = µ b (p,T) Energi bebas G = f (P, T, n1, n2) Turunkan untuk mendapatkan definisi : POTENSIAL KIMIA ( µ)

7. Phase Boundaries Boiling Points Temperature at which vapor pressure equals external pressure Normal boiling point (T b ) external pressure = 1 atm (H 2 O: 100.0°C) Standard boiling point external pressure = 1 bar (0.987 atm) (H 2 O: 99.6°C)

8. Phase Boundaries Melting Points Melting temperature both solid and liquid phases exist. Equivalent to freezing temperature Normal freezing (melting) point (T f ) external pressure = 1 atm (H 2 O: 0°C) Standard freezing point external pressure = 1 bar (0.987 atm)

9. Phase Boundaries Triple Point (T 3 ) - place at which 3 phase boundaries meet All 3 phases exist simultaneously Typically solid, liquid and gas Lowest pressure and temperature liquid can exist Invariant, property of substance (H 2 O: 273.15K, 6.11 mbar )

10. Phase Boundaries p c T b 1 atm = p ex supercritical fluid

11. Phase Boundaries Critical Point In closed vessel boiling does not occur. Pressure increases and fluid level drops. r liquid decreases and r vapor increase as T increases At some point r liquid = r vapor and boundary disappears: critical temperature ( T c ),vapor pressure is critical pressure , p c Above a single uniform phase exists, supercritical fluid Highest temperature liquid can exist

12. Phase Diagram of WATER Slope of solid-liquid boundary means large D p necessary to significantly change melting temp. Negative slope means T melt decreases as p increase Due to structure of water Liquid has lower volume than solid ( r liquid > r solid ) Ice VI,VII, VIII 21 kbar, ~5 °C Ice VI,VII, liquid 22 kbar, 81.6 °C

13. Phase Diagram of WATER High pressure phases Different crystal structure and density Ice I (hexagonal); Ice III (Tetragonal) At -175°C and 1 atm: Ice I ( r = 0.94 g/cc); Ice VI ( r = 1.31 g/cc); Can melt at higher temperatures than Ice I Ice VII melts at 100°C but only exists at p>25 kbar 8 triple points (6 plotted) Only one between solid (Ice I), liquid and gas Ice VI,VII, VIII 21 kbar, ~5 °C Ice VI,VII, liquid 22 kbar, 81.6 °C

14. Phase Diagram of CO2 Melting temperature increases a p increases Unlike water& more typical T 3 > 1 atm Liquid CO 2 doesn’t exist at 1 atm High pressure CO 2 tanks contain liquid At 25°C (298.15 K) and 67 atm, gas and liquid co-exist

15. Phase Diagram of He Note temperature scale (< 6K) Solid and gas never in equilibrium Two liquid phases Phase boundary l -line (type of phase transition) Higher temperature liquid (He-I) is regular liquid Low temperature liquid (He-II) superfluid (zero viscosity) It rather than solid exists close to 0K 3 He 4 He

16. Phase Diagram of He 3 He 4 He Phase diagram depends on nuclear spin 3 H - non-zero spin, 4 H -zero spin 3 H diagram different than 4 3 H, esp. low temperature 3 H S liquid < S solid , melting exothermic