Chapter Twelve Notes - Chapter 12 The Laws of...

Info icon This preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 12: The Laws of Thermodynamics I) Energy can be transferred to a system by heat and by work done on the system A) The work done on a gas at constant pressure (isobaric process) is :  1) W=-P Δ V 2) Work done by the gas on its environment is the negative of this B) The area under the graph in a PV diagram is equal in magnitude to the work done on the gas 1) If the arrow on the graph points towards larger volumes, the work done on the gas is negative 2) If the arrow on the graph points towards small volumes the work done on the gas is positive II) First law of thermodynamics: if a system undergoes a change from an initial state to a final state, where Q is the  energy transferred to the system by heat and W is the work done on the system, the change in internal energy of  the system  Δ U, is:  Δ U=Q+W A) Q is positive when energy is transferred into the system by heat B) Q is negative when energy is transferred out of the system by heat C) Internal energy of any isolated system must remain constant ( Δ U=0) D) Change in internal energy of an ideal gas is  Δ U=nC v Δ T III) Molar specific heat at constant volume of a monatomic gas, C v : is C v =3/2R A) Value depends on the gas and varies with temperature and pressure 1) Larger molar specific heat requires more energy to realize a given temperature change 2) Size depends on structure of the gas molecules and how many different ways it can store energy B) Degree of freedom: Each different way a gas molecule can store energy.  Contribute  ½  R to the molar  specific heat IV) Isobaric process: pressure remains constant as the gas expands or is compressed A) The temperature of an expanding gas must decrease as the internal energy decreases B) Q = nC p Δ 1) C P =5/2R  2) For ideal gases the molar heat capacity at constant pressure., C p  is the sum of the molar heat capacity  at constant volume C v  and the gas constant R: C P  = C V  + R V) Adiabatic process: no energy enters or leaves the system by heat A) System is insulated B) System is only thermally insulated not mechanically insulated (can still do work) C) Δ U=W because Q=0 D) Adiabatic index o the gas:  =C γ p /C v E) If a hot gas is allowed to expand so quickly that there is no time for energy to enter or leave the system by  heat, the work done on the gas is negative and the internal energy decreases b/c kinetic energy is  transferred from the gas molecules to the moving piston
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern