Temperature Scales, Absolute Zero • Phase Changes

Total Page：16

File Type：pdf, Size：1020Kb

Lecture 13 • Temperature scales, absolute zero • Phase changes, equilibrium, diagram • Ideal gas model Temperature • temperature is related to system’s thermal energy (kinetic and potential energy of atoms) • measured by thermometer: small system undergoes a change upon exchagning thermal energy, e.g., length of mercury/alcohol in glass tube or ideal gas’ pressure Temperature Scales • Celcius/centigrade scale: boiling point (100 C ) freezing point (0 C ) ◦ ◦ T = 9 T + 32 • Fahrenheit scale: F 5 C ◦ F (212 ◦ and 32 ◦ F ) Absolute Zero and Absolute Temperature • property changes linearly with temperature: e.g., pressure of constant-volume gas p = 0 for all gases at T = 273 C • 0 ◦ p due to collisions all motion− stopped, zero thermal energy: absolute zero (lowest temperature) • absolute temperature scale: zero point at absolute zero Kelvin scale if same unit size as Celcius scale: TK = TC + 273 (no degrees for Kelvin) Phase Changes • melting/freezing point: temperature at which solid becomes liquid...thermal energy large enough to allow molecules to move around • phase equilibrium: 2 phases co-exist • condensation/boiling point: phase equilibrium between liquid and gas thermal energy too large for bonding • phase change temperatures are pressure-dependent: freezing (boiling) point higher (lower) at lower pressure Phase diagram • how phases and phase changes vary with T, p • 3 regions with phase transitions at boundaries...gas-solid (sublimation) • critical point: liquid-gas boundary ends • triple point: all 3 phases co-exist • triple point of water ( T =0 . 01 C ) used as reference 3 ◦ point (reproduced with no variation) for Kelvin scale: 273.16 K 0 K ﬁxed by gas properties • cf. Celcius scale requires 2 reference points: boiling and melting points (p-dependent) Ideal Gases • (strong) repulsive forces between atoms (incompressibility of solids/liquids + (weak) attractive forces (tensile strength of solids; cohesion of liquid droplets) r • solids and liquids: atomic separation ∼ eq gases: average r r eq freely moving • ! till collide (steep wall for r < r eq. important) • Ideal gas model: hard non-interacting spheres, bounce on contact • good for low density and T condensation point ! (both mono and d-atomic gases).

Copy Link

Recommended publications

On the Definition of the Measurement Unit for Extreme Quantity Values: Some Considerations on the Case of Temperature and the Kelvin Scale
ON THE DEFINITION OF THE MEASUREMENT UNIT FOR EXTREME QUANTITY VALUES: SOME CONSIDERATIONS ON THE CASE OF TEMPERATURE AND THE KELVIN SCALE Franco Pavese 1 1 Torino, Italy E-mail (corresponding author): [email protected] Abstract Many quantities are attributed a range of values that can apparently extend to infinity (on one side or both sides). In this respect, the definitions of their measurement units do not place any constraint to the maximum (or minimum) value for their validity. In general, that happens because those extreme values are far from being reached on the earth, or presently in experiments. However, since the same units are used also in fields of physics, chemistry or technology where they could occur—namely in the description of the universe in one sense, and in pico-nanoscale or particle physics in another sense—the issue of extreme values (not in statistical meaning here) is not irrelevant. The question placed and discussed in this paper is whether the present kelvin scale, based on Lord Kelvin’s second definition (our currently accepted concept of temperature), applies over a full range between bounds (0, ∞) or not, and about the concept of temperature in itself in the extremes regions. The aim, however, is not to provide an answer, but to suggest there are difficulties with the application of current concepts at extremes of temperature. Keywords: kelvin scale; Lord Kelvin proposals; extreme temperatures; temperature definition; unit definition 1 Introduction Many quantities have a range of values that can apparently extend to infinity (on one side or both sides). In this respect, the definition of their measurement units does not place any constraint to the maximum (or minimum) value for its validity.
[Show full text]
The Third Law of Thermodynamics Or an Absolute Definition for Entropy. Part
The third law of thermodynamics or an absolute definition for Entropy. Part 1 : the origin and applications in thermodynamics. Accepted for the revue: “La Météorologie ” / Revision 2 - December 2, 2019. by Pascal Marquet. Météo-France, CNRM/GMAP, Toulouse. Abstract This article describes the third law of thermodynamics. This law is often poorly known and is often decried, or even considered optional and irrelevant to describe weather and climate phenomena. This, however, is inaccurate and contrary to scientific facts. A rather exhaustive historical study is proposed here in order to better understand, in another article to come, why the third principle can be interesting for the atmosphere sciences. 1 Introduction Before being able to study in a second part the properties of entropy in the atmosphere, it is necessary to recall in this first part why its calculation poses certain problems in thermodynamics, problems whose solution passes through the invention and the application of the third law of thermodynamics which introduces a kind of absolute in the calculation of entropy. And the idea that certain absolutes may exist had preceded the establishment of the third law. 2 The notion of absolute temperature Thermodynamics teaches us that the notion of temperature corresponds to the measurement of the energy of the microscopic agitations of atoms or molecules in the solids, liquids or gases which constitute the environment which surrounds us, and therefore in particular in the atmosphere. Carnot (1824) was able to establish the existence of universal things, supposing that the perpetual motion of thermal machines was impossible. He first highlighted the existence of a maximum efficiency that depends only on the temperatures of the bodies between which these machines operate.
[Show full text]
UBO & MPD Glossary
UBO & MPD Glossary December 2011 Aniline Point – The aromatics content of a hydrocarbon A. mixture. Abnormal Pressure - Reservoir pore fluid pressure that Annulus Friction Pressure (AFP) – Difference is not similar to normal saltwater gradient pressure. The between bottomhole pressure and choke pressure due to term is usually associated with higher than normal friction; a function of flow rate, hole geometry, surface pressure, increased complexity for the well designer and roughness, fluid properties. an increased risk of well control problems. Abnormal – American Petroleum Institute. pressure gradients exceed a 10-ppg equivalent fluid API density (0.52 psi per foot). Gradients below normal are API Gravity - arbitrary measurement of density adopted in called subnormal. 1921 by the American Petroleum Institute and the Bureau Absolute Pressure - pressure measured with respect to of Standards. zero pressure; the sum of atmospheric pressure and gauge Apparent Power - combination of real and reactive pressure. power. Absolute Temperature - temperature measured with Apparent Viscosity - Slope of the shear stress versus respect to absolute zero, in degrees Rankine or degrees velocity gradient for a fluid. For Newtonian fluids, the Kelvin. apparent viscosity equals the absolute viscosity. Absolute Viscosity - dynamic relationship between a Aromatics – Ring group chemical structure. Most force and the fluid motion. common are benzene, toluene, and xylene. Absolute Zero Temperature - temperature that B. prevents molecular motion. Back Pressure Valve - A flow control valve to provide - rate of change in velocity. Acceleration backflow control when running or pulling a string. Active data - continually updated data, based on latest Backup – Redundant equipment available to complete an operational data. operation in the event the primary equipment fails.
[Show full text]
Thermodynamics the Study of the Transformations of Energy from One Form Into Another
Thermodynamics the study of the transformations of energy from one form into another First Law: Heat and Work are both forms of Energy. in any process, Energy can be changed from one form to another (including heat and work), but it is never created or distroyed: Conservation of Energy Second Law: Entropy is a measure of disorder; Entropy of an isolated system Increases in any spontaneous process. OR This law also predicts that the entropy of an isolated system always increases with time. Third Law: The entropy of a perfect crystal approaches zero as temperature approaches absolute zero. ©2010, 2008, 2005, 2002 by P. W. Atkins and L. L. Jones ©2010, 2008, 2005, 2002 by P. W. Atkins and L. L. Jones A Molecular Interlude: Internal Energy, U, from translation, rotation, vibration •Utranslation = 3/2 × nRT •Urotation = nRT (for linear molecules) or •Urotation = 3/2 × nRT (for nonlinear molecules) •At room temperature, the vibrational contribution is small (it is of course zero for monatomic gas at any temperature). At some high temperature, it is (3N-5)nR for linear and (3N-6)nR for nolinear molecules (N = number of atoms in the molecule. Enthalpy H = U + PV Enthalpy is a state function and at constant pressure: ∆H = ∆U + P∆V and ∆H = q At constant pressure, the change in enthalpy is equal to the heat released or absorbed by the system. Exothermic: ∆H < 0 Endothermic: ∆H > 0 Thermoneutral: ∆H = 0 Enthalpy of Physical Changes For phase transfers at constant pressure Vaporization: ∆Hvap = Hvapor – Hliquid Melting (fusion): ∆Hfus = Hliquid –
[Show full text]
Lecture 15 November 7, 2019 1 / 26 Counting
...Thermodynamics Positive specific heats and compressibility Negative elastic moduli and auxetic materials Clausius Clapeyron Relation for Phase boundary \Phase" defined by discontinuities in state variables Gibbs-Helmholtz equation to calculate G Lecture 15 November 7, 2019 1 / 26 Counting There are five laws of Thermodynamics. 5,4,3,2 ... ? Laws of Thermodynamics 2, 1, 0, 3, and ? Lecture 15 November 7, 2019 2 / 26 Third Law What is the entropy at absolute zero? Z T dQ S = + S0 0 T Unless S = 0 defined, ratios of entropies S1=S2 are meaningless. Lecture 15 November 7, 2019 3 / 26 The Nernst Heat Theorem (1926) Consider a system undergoing a pro- cess between initial and final equilibrium states as a result of external influences, such as pressure. The system experiences a change in entropy, and the change tends to zero as the temperature char- acterising the process tends to zero. Lecture 15 November 7, 2019 4 / 26 Nernst Heat Theorem: based on Experimental observation For any exothermic isothermal chemical process. ∆H increases with T, ∆G decreases with T. He postulated that at T=0, ∆G = ∆H ∆G = Gf − Gi = ∆H − ∆(TS) = Hf − Hi − T (Sf − Si ) = ∆H − T ∆S So from Nernst's observation d (∆H − ∆G) ! 0 =) ∆S ! 0 As T ! 0, observed that dT ∆G ! ∆H asymptotically Lecture 15 November 7, 2019 5 / 26 ITMA Planck statement of the Third Law: The entropy of all perfect crystals is the same at absolute zero, and may be taken to be zero. Lecture 15 November 7, 2019 6 / 26 Planck Third Law All perfect crystals have the same entropy at T = 0.
[Show full text]
Ch. 3. the Third Law of Thermodynamics (Pdf)
3-1 CHAPTER 3 THE THIRD LAW OF THERMODYNAMICS1 In sharp contrast to the first two laws, the third law of thermodynamics can be characterized by diverse expression2, disputed descent, and questioned authority.3 Since first advanced by Nernst4 in 1906 as the Heat Theorem, its thermodynamic status has been controversial; its usefulness, however, is unquestioned. 3.1 THE HEAT THEOREM The Heat Theorem was first proposed as an empirical generalization based on the temperature dependence of the internal energy change, ∆U, and the Helmholtz free energy change, ∆A, for chemical reactions involving condensed phases. As the absolute temperature, T, approaches zero, ∆U and ∆A by definition become equal, but The Heat Theorem stated that d∆U/dT and d∆A/dT also approach zero. These derivatives are ∆Cv and -∆S respectively. The statement that ∆Cv equals zero would attract little attention today in view of the abundance of experimental and theoretical evidence showing that the heat capacities of condensed phases approach zero as zero absolute temperature is approached. However, even today the controversial and enigmatic aspect of The Heat Theorem is the equivalent statement 1 Most of this chapter is taken from B.G. Kyle, Chem. Eng. Ed., 28(3), 176 (1994). 2 For a sampling of expressions see E. M. Loebl, J. Chem. Educ., 37, 361 (1960). 3 For extreme positions see E. D. Eastman, Chem. Rev., 18, 257 (1936). 4 All of Nernst's work in this area is covered in W. Nernst, The New Heat Theorem; Dutton: New York, 1926. 3-2 lim ∆S = 0 (3-1) T → 0 In 1912 Nernst offered a proof that the unattainability of zero absolute temperature was dictated by the second law of thermodynamics and was able to show that Eq.
[Show full text]
MODULE 11: GLOSSARY and CONVERSIONS Cell Engines
Hydrogen Fuel MODULE 11: GLOSSARY AND CONVERSIONS Cell Engines CONTENTS 11.1 GLOSSARY.......................................................................................................... 11-1 11.2 MEASUREMENT SYSTEMS .................................................................................. 11-31 11.3 CONVERSION TABLE .......................................................................................... 11-33 Hydrogen Fuel Cell Engines and Related Technologies: Rev 0, December 2001 Hydrogen Fuel MODULE 11: GLOSSARY AND CONVERSIONS Cell Engines OBJECTIVES This module is for reference only. Hydrogen Fuel Cell Engines and Related Technologies: Rev 0, December 2001 PAGE 11-1 Hydrogen Fuel Cell Engines MODULE 11: GLOSSARY AND CONVERSIONS 11.1 Glossary This glossary covers words, phrases, and acronyms that are used with fuel cell engines and hydrogen fueled vehicles. Some words may have different meanings when used in other contexts. There are variations in the use of periods and capitalization for abbrevia- tions, acronyms and standard measures. The terms in this glossary are pre- sented without periods. ABNORMAL COMBUSTION – Combustion in which knock, pre-ignition, run- on or surface ignition occurs; combustion that does not proceed in the nor- mal way (where the flame front is initiated by the spark and proceeds throughout the combustion chamber smoothly and without detonation). ABSOLUTE PRESSURE – Pressure shown on the pressure gauge plus at- mospheric pressure (psia). At sea level atmospheric pressure is 14.7 psia. Use absolute pressure in compressor calculations and when using the ideal gas law. See also psi and psig. ABSOLUTE TEMPERATURE – Temperature scale with absolute zero as the zero of the scale. In standard, the absolute temperature is the temperature in ºF plus 460, or in metric it is the temperature in ºC plus 273. Absolute zero is referred to as Rankine or r, and in metric as Kelvin or K.
[Show full text]
Section 5 Further Thermodynamics
Section 5 Further Thermodynamics 5.1 Phase equilibrium 5.1.1 Conditions for equilibrium coexistence It is an observed fact that the physical state of a system can sometimes be changed dramatically when its external conditions are changed only slightly. Thus ice melts when the temperature is increased from slightly below 0°C to slightly above this temperature. Different physical states of the same substance are referred to as phases and the study of transitions between phases is one of the most interesting problems in statistical thermodynamics. This is partly because the question of predicting when and how a phase transition will occur is still not a fully solved problem. There is the further point that a comprehensive understanding of phase transition phenomena might have wider application to such things as the outbreak of a war or a stock market crash. Very generally, phase transitions are due to interactions between the constituent particles of a system. The model-dependence of the behavior would suggest that full understanding can only come from a statistical mechanical study, not from thermodynamics. However there are many aspects of phase transitions which seem to be general and common to many systems. Macroscopic thermodynamics is of help here since it is model-independent and it connects seemingly unrelated properties of the system. This frees us to concentrate on the few thermodynamic variables of the system instead of getting bogged down in the microscopic detail. We start by considering the conditions for equilibrium to exist between two phases of the same substance — such as ice and water, for example.
[Show full text]
Visualizing Bose-Einstein Condensates
VISUALIZATIONV ISUALIZATION C ORNER Editor: Jim X. Chen, [email protected] VISUALIZING BOSE–EINSTEIN CONDENSATES By Peter M. Ketcham and David L. Feder OSE–EINSTEIN CONDENSATES ARE THE COLDEST SUB- ity to do so, and the result is the for- mation of tiny quantum vortices, each B STANCES EVER MADE. ALONG WITH THIS DISTINCTION, with a quantized amount of superﬂow around it. BECS HAVE OTHER INTRIGUING PROPERTIES: FOR EXAMPLE, THEY These quantum whirlpools are pro- duced in BECs by rotating the mag- BEHAVE MUCH LIKE LIGHT DOES IN AN OPTICAL FIBER. IN FACT, netic trap in which the BEC is con- tained—much like trying to stir your many research groups have produced Quantum Vortices coffee by squeezing the cup and spin- “atom lasers” formed from traveling Laboratory-produced BECs aren’t ning yourself around. BECs range BECs. They also behave similarly to quite as simple as the ones Bose and from a millimeter to a centimeter in superﬂuids, much like liquid helium or Einstein originally predicted because size, so you’d think it should be easy to superconductors. By studying BECs, they are made from real alkali atoms, detect the vortices simply by shining we’ve gained important insights into not ideal gases. For instance, unlike an light on the cloud, taking a photo- much more complicated, but closely ideal gas, atoms can’t pass through one graph, and noting the tiny holes in the related, systems. another. They interact strongly, and at- picture where the atom density has BECs created from dilute alkali va- tract each other if they get too close to- gone to zero in the vortex cores.
[Show full text]
Absolute Zero Summative Evaluation
Absolute Zero Summative Evaluation PREPARED BY Marianne McPherson, M.S., M.A. Laura Houseman Irene F. Goodman, Ed.D. SUBMITTED TO Meredith Burch, Meridian Productions, Inc. Linda Devillier, Devillier Communications, Inc. Professor Russell Donnelly, University of Oregon October 2008 GOODMAN RESEARCH GROUP, INC. August 2003 1 ACKNOWLEDGMENTS GRG acknowledges the following individuals for their contributions to the Absolute Zero summative evaluation: • Professor Russell Donnelly at the University of Oregon, Linda Devillier of Devillier Communications, Inc., and Meredith Burch of Meridian Productions Inc. for their supportive collaboration; • GRG assistants Nina Grant, Stephanie Lewis, Theresa Rowley, and Zoe Shei for data entry and coordination of the evaluation of outreach materials; • The adult and student viewers who participated in the evaluation of the television series, and the teachers who evaluated the outreach materials; • The National Partners, Participants, and Absolute Zero Experts who participated in the survey and interviews. This report was written under contract to University of Oregon, National Science Foundation grant # 0307939. The views expressed are solely those of Goodman Research Group, Inc. GOODMAN RESEARCH GROUP, INC. October 2008 TABLE OF CONTENTS Executive Summary......................................................................................... i Introduction..................................................................................................... 1 Methods .........................................................................................................
[Show full text]
Thermodynamic Temperature
Thermodynamic temperature Thermodynamic temperature is the absolute measure 1 Overview of temperature and is one of the principal parameters of thermodynamics. Temperature is a measure of the random submicroscopic Thermodynamic temperature is defined by the third law motions and vibrations of the particle constituents of of thermodynamics in which the theoretically lowest tem- matter. These motions comprise the internal energy of perature is the null or zero point. At this point, absolute a substance. More specifically, the thermodynamic tem- zero, the particle constituents of matter have minimal perature of any bulk quantity of matter is the measure motion and can become no colder.[1][2] In the quantum- of the average kinetic energy per classical (i.e., non- mechanical description, matter at absolute zero is in its quantum) degree of freedom of its constituent particles. ground state, which is its state of lowest energy. Thermo- “Translational motions” are almost always in the classical dynamic temperature is often also called absolute tem- regime. Translational motions are ordinary, whole-body perature, for two reasons: one, proposed by Kelvin, that movements in three-dimensional space in which particles it does not depend on the properties of a particular mate- move about and exchange energy in collisions. Figure 1 rial; two that it refers to an absolute zero according to the below shows translational motion in gases; Figure 4 be- properties of the ideal gas. low shows translational motion in solids. Thermodynamic temperature’s null point, absolute zero, is the temperature The International System of Units specifies a particular at which the particle constituents of matter are as close as scale for thermodynamic temperature.
[Show full text]
Glossary of Energy Terms
Glossary of Standard Energy Auditing Terms Absolute Pressure Gauge pressure plus atmospheric pressure. Absolute Temperature Temperature measured from absolute zero. Absolute Zero Temperature Temperature at which all molecular motion ceases(-460 F. and -273 C.) Absorbent Substance with the ability to take up or absorb another substance. Absorption Refrigerator Refrigerator which creates low temperature by using the cooling effect formed when a refrigerant is absorbed by chemical substance. ACCA A leading HVAC/R Association - http://www.acca.org/ Accumulator Storage tank which receives liquid refrigerant from evaporator and prevents it from flowing into suction line before vaporizing. ACH, Air Changes Per Hour The number of times that air in a house is completely replaced with outdoor air in one hour. Actuator That portion of a regulating valve which converts mechanical fluid, thermal energy or electrical energy into mechanical motion to open or close the valve seats. Add On Heat Pump Installing a heat pump in conjunction with an existing fossil fuel furnace. Adiabatic Compression Compressing refrigerant gas without removing or adding heat. Adsorbent Substance with the property to hold molecules of fluids without causing a chemical or physical damage. Aeration Act of combining substance with air. AFUE Annual Fuel Utilization Efficiency -ratio of annual output of useful energy or heat to the annual energy input to the furnace Agitator Device used to cause motion in confined fluid. AHU (Air Handler Unit) The inside part of the A/C system that contains the blower, cooling (evaporator) coil, and heater. Air Change Page 134 of 149 The amount of air required to completely replace the air in a room or building; not to be confused with recirculated air Air Cleaner Device used for removal of airborne impurities.
[Show full text]