1 / 19

Understanding Ideal Gas Law: Phase Change and Heat Calculations in Physics

In this lecture by Professor Lee Carkner, we explore the Ideal Gas Law and its implications in real-world scenarios, such as cooling processes. We delve into calculations involving heat transfer (Q) during phase changes, and analyze various temperature points (from -2.8°C to -18°C) to illustrate these concepts. Key discussions include characteristics of ideal gases, internal energy, and gas mixtures. By examining pressure, volume, and temperature relationships, we shed light on the behavior and properties of gases in different states and how they deviate from ideality.

anthea
Télécharger la présentation

Understanding Ideal Gas Law: Phase Change and Heat Calculations in Physics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Ideal Gas Law Physics 313 Professor Lee Carkner Lecture 10

  2. Exercise #9 -- Chicken • Cool to -2.8C: • Q1 = cmDT = (3.32)(50)(8.8) = • Phase change: • Q2 = Lm = (247)(5) = • Cool to -18 C: • Q3 = (1.77)(50)(15.2) = • Cool box to -18 C: • Q4 = (1.4)(1.5)(24) = • Sum all heats: • QT = Q1 + Q2 + Q3 + Q4 = • Most heat lost for phase change

  3. Ideal Gas • What is an ideal gas? • The properties converge to common values as P goes to zero • An ideal gas is any gas at the limit of zero pressure

  4. Approaching Zero Pressure • The equation of state of a gas depends on T, P and V • We know that for constant V: • Can express Pv relationship by virial expansion: • Experiment reveals that for constant T: • A is function of T only

  5. Equation of State: Ideal Gas • Combining equations • We can write the constant part of this equation as: • The equation of state for any gas as pressure approaches zero is:

  6. Internal Energy • What does the internal energy depend on? • For a real gas U is dependant on P (U/P)T = 0 [as P goes to 0]

  7. Ideal Gas Relations • For an ideal gas: PV = nRT • Internal energy is a function of the temperature only

  8. Ideal and Real Gas • Real gases deviate from ideal ones with pressure • We can express the deviation from ideal gas behavior with the compressibililty factor, Z • For an ideal gas: Pv = RT • For a real gas: Pv = ZRT • z = 1 for ideal gasses

  9. Critical Point • What determines if a gas is at high or low pressure? • The point where there is no difference between liquid and gas • The critical point is defined by a critical volume, pressure and temperature (VC,PC,TC)

  10. Gas Mixtures • e.g. air • How is P,V and T for the mixture related to the properties of the individual gasses?

  11. Mixture Laws • Dalton’s Law: Pm = S Pi (Tm,Vm) • Amagat’s Law: Vm = S Vi(Tm,Pm) • Strictly true only for ideal gases

  12. Mixture Properties Zm = S yiZi • Where yi is the mole fraction (yi = ni/nm) PmVm = ZmnmRTm • It may be hard to determine Zi

  13. First Law for Ideal Gas dU = dQ + dW dW = -PdV • At constant volume: • Since U depends only on T: dQ = CVdT + PdV

  14. Constant Pressure PV = nRT dQ = CVdT + nRdT -VdP • At constant pressure: • Molar heat capacity: cP = cV + R

  15. Forms of the First Law • For an ideal gas: dU = dQ = dQ = dQ =

  16. Heat Capacities • For an ideal gas: • For monatomic gas: • For any gas:

More Related