ME 10.311 Thermo I Lect 3.docx Page 1 of 4
Lect. 3 : Molec Energy, Temperature, and Pure Subst. Delivery Notes:
Class L.O.: 1. Initially draw the pressure scale 1. Able to describe what Energy is to a RU freshmen and describe three diagram, before primary forms of energy, from a molec. level. class starts 2. Able to describe what the temperature equality and zeroth law mean 3. Able to describe various temperature scales Temperature Scale “An upside down F” 4. Able to explain the temperature and volume behavior of a pure substance under constant pressure. 5. Able to interpret the various phase regions on a phase diagram
6. Able to explain and calculate quality
Class M.Map:
P_abs = P_atm +P_gauge
2. Lect 2 quick review. .
ALE = active learning exercise. TPS = think pair shair
ALE Rowan Power Tour Minute Paper: Two ideas that “stuck” in your mind. Å Minute Paper
Topic 1: Molecular forms of energy
General Comments Regarding Energy
• Energy = ability to produce an effect ( it’s a scalar!)
How do you think • Energy is a mathematical abstraction – it only exists as it relates to other energy – at the variables we can measure – KE or PE, for example molecular level in a fluid - is stored?
Î Chambers w/ Diff. Temperatures before & after mixing
ME 10.311 Thermo I Lect 3.docx Page 2 of 4
PRIMARY FORMS OF INTERNAL ENERGY, symbol U or u
Draw. monatomic:
helium, neon, argon, krypton, xenon and radon.
What forms of energy come to mind?
hydrogen, nitrogen, oxygen, and carbon monoxide.
1. Intermolecular – assoc. w/ forces betw molec. – hard to determine, depends on molec position with time.
2. Molecular Kinetic Energy – dep. mass and velocity of structure.
3. Intramolecular – depends on molecular & atomic structure Î Symbol indicates a slide is used Î Chamber with more complex Molecules
Topic 2: Temperature Equality
• Temperature reflects molecular activity / energy
• Temperature Equality Æ two substances brought in contact with each other undergoe no property changes (macro) over time. o At this pt we say that the average translational K.E. of their molecules is equivalent. o It does not mean that their internal energy is equivalent since energy is stored in other forms….say vibrational If time – show applet What did you observe? Note: Questions 1-4 in Î Show Applet for “intuitive feel” for thermal equilibrium applet
If time: Compare Experiments #1 to #4. Why?
ME 10.311 Thermo I Lect 3.docx Page 3 of 4 • Zeroth law: TRANSITIVE THEORY FOR TEMPERATURE – RULE OF LAW FOR CALIBRATION
If T_a = T_c and if T_b = T_c , then T_a = T_b
Topic 3: Temperature Scales ( A primary unit)
• SI Units o o Celcius Scale: C – based on water, ice and steam point at 1atm (~101 kpa) o o Kelvin Scale: K = C + 273.15 Absolute Scale Thermodynamic Scale ( indep. of mat.)
• English Engineering Units o Fahrenheit Scale: oC*(9/5) +32, also based on
water, ice and steam at 1 atm (14.7 psia) o Rankine Scale: oF + 459.67
Abs. Scale Thermo Scale (indep. of mat.) Suggest Video Clip – Absolute ***** END OF CHAPTER 2 ******* Zero.
Chapter 3 Topic 4: Pure Substance Properties and Behavior [S 4] “Write this down in your notes.”
1. “Pure” = homog. and constant chemical composition in all phases
Water Nitrogen When do you think air Air ….sometimes might not be assumed pure? 2. “Simple compressible subst.” (SCS) = no surface, magnetic, or electrical effects.
3. “Vapor-pressure curve” --- assumes we can increase pressure
Æ “Saturation temperature” = temp. at which vaporization takes place at a given pressure. “Saturation pressure” = press. at which vaporization takes place at a ME 10.311 Thermo I Lect 3.docx Page 4 of 4 given temperature. Many ways to find: tables or computers (EES)
4. “Temperature-Volume” [ Æ ] Diagram for Water (Fig. 3.3) Key Elements Consider this constant pressure process: o Saturated liquid line o Saturated vapor line o Critical point o Isobaric Lines Pg 487 contents o Superheated Vapor Pg 510 SI table Pg 588 english o Subcooled or Compressed liquids o Quality Å KEY FIGURE!! CONSTANT VOLUME PROCESS [ S 8 ] --- A.L.E, TPS handout
5. “Vapor quality” or “quality” [Æ ]
mmvapor vapor x == mm+ m liquid vapor mix vv=+ xv ffg “state” = location on diagram 6. “ Independent Properties” + rem: T&P not • Properties that are able to define the specific state of a substance sufficient with 2-ph. on a phase diagram ( P vs. T, T vs. v, and P vs. v). For air, if remains • For pure substances, the minimum number of properties is two. gasous, only two properties are needed
NEXT TIME – phase diagrams & several examples
Homework (including reading, writing, and problems)
See W.I.P