Devil physics The baddest class on campus IB Physics-2

1. Devil physicsThe baddest class on campusIB Physics-2

2. Tsokos Lesson 3-3ideal gases

3. IB Assessment Statements Topic 10.2., Thermal Physics: Processes 10.2.1. Deduce an expression for the work involved in a volume change of a gas at constant pressure. 10.2.2. State the first law of thermodynamics. 10.2.3. Identify the first law of thermodynamics as a statement of the principle of energy conservation.

4. IB Assessment Statements Topic 10.2., Thermal Physics: Processes 10.2.4. Describe the isochoric (isovolumetric), isobaric, isothermal and adiabatic changes of state of an ideal gas. 10.2.5. Draw and annotate thermodynamic processes and cycles on P-V diagrams.

5. IB Assessment Statements Topic 10.2., Thermal Physics: Processes 10.2.6. Calculate from a P-V diagram the work done in a thermodynamic cycle. 10.2.7. Solve problems involving state changes of a gas.

6. Objectives • State the definition of pressure, P = F/A • Understand that an ideal gas is a gas in which the molecules do not exert forces on each other except when colliding • Understand that an ideal gas obeys the law, PV = nRTat all pressures, temperatures and volumes

7. Objectives • Understand the ideal gas law and solve problems using it • Appreciate that pressure in a gas develops as a result of collisions between the molecules and the walls of the container in which the momentum of the molecules changes

8. Video – Developing the Gas Laws

9. Pressure • Force per unit area • Only the force normal to the area • Unit is the Pascal (Pa) or Nm-2 • Atmospheric pressure is 1.013 x 105 Pa

10. Moles of Gases • Convenient to use moles (not the furry kind) • Avogadro's Avocado number • Atomic Mass = Molar Mass = grams/mol

11. Moles of Gases • The number of moles can be found by dividing the number of molecules, N, by the Avogadro's Avocado number • Also found by dividing the mass of the gas in grams by the Atomic / Molar Mass

12. Boyle-Mariotte Law • At constant temperature and with a constant quantity of gas, pressure is inversely proportional to volume • The graph of pressure versus volume is a hyperbola, aka an isothermal curve

13. Volume-Temperature Law • When the temperature is expressed in Kelvin and pressure is kept constant, volume and temperature are proportional to each other

14. Volume-Temperature Law • When the temperature is expressed in Kelvin and pressure is kept constant, volume and temperature are proportional to each other Graph of different quantities of the same gas or same gas at different pressures

15. Pressure-Temperature Law • When the temperature is expressed in Kelvin and volume is kept constant, pressure and temperature are proportional to each other

16. Pressure-Temperature Law • When the temperature is expressed in Kelvin and volume is kept constant, pressure and temperature are proportional to each other

17. Equation of State

18. Ideal Gas Law • An ideal gas will obey this law at all temperatures, pressures and volumes. • Real gases obey this law only for a certain range of temperatures, pressures and volumes.

19. Σary Review • Can you state the definition of pressure, P = F/A? • Do you understand that an ideal gas is a gas in which the molecules do not exert forces on each other except when colliding? • Do you understand that an ideal gas obeys the law, PV = nRTat all pressures, temperatures and volumes?

20. Σary Review • Do you understand the ideal gas law and can you solve problems using it? • Do you appreciate that pressure in a gas develops as a result of collisions between the molecules and the walls of the container in which the momentum of the molecules changes?

21. IB Assessment Statements Topic 10.2., Thermal Physics: Processes 10.2.1. Deduce an expression for the work involved in a volume change of a gas at constant pressure. 10.2.2. State the first law of thermodynamics. 10.2.3. Identify the first law of thermodynamics as a statement of the principle of energy conservation.

22. IB Assessment Statements Topic 10.2., Thermal Physics: Processes 10.2.4. Describe the isochoric (isovolumetric), isobaric, isothermal and adiabatic changes of state of an ideal gas. 10.2.5. Draw and annotate thermodynamic processes and cycles on P-V diagrams.

23. IB Assessment Statements Topic 10.2., Thermal Physics: Processes 10.2.6. Calculate from a P-V diagram the work done in a thermodynamic cycle. 10.2.7. Solve problems involving state changes of a gas.

24. Questions

25. Homework #1-19