17 Temperature and Kinetic Theory

1. 17 Temperature and Kinetic Theory • Thermal Equilibrium and Temperature • Gas Thermometers and Absolute Temperature • The Ideal Gas Law • The Kinetic Theory of Gases • Hk: 15, 33, 39.

2. Temperature & Energy • temperature: a measurement of the average KE per molecule • thermal energy: the kinetic energy resulting from the random movement of atoms and molecules • absolute temperature scale: a scale in which the temperature is proportional to the thermal energy. Has true zero.

3. Thermal Equilibrium • thermometric property: A physical property that changes with temperature, e.g. volume. • thermal equilibrium: zero net heat flow while in thermal contact • 0th Law 

4. 0 0th Law

5. 0 Celsius Fahrenheit Conversions

6. 0 Absolute Kelvin Scale

7. Ideal Gases • N molecules (few intermolecular collisions, no long range forces) • v = average speed • P due to wall-collisions (P ~ Nv/t) • t = time between same-wall collision

8. Ideal gas pressure

9. Ideal Gas Law

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11. Gas Thermometer PV ~ NT P ~ T Gas cools, avg. KE  0, (absolute zero), P  0, ≈ -273 °C 11

12. Ex. Constant Pressure process on an Ideal Gas What % increase in V occurs for an ideal gas heated from 20C to 40C? (V ~ T) (It does not double, b/c C is not a thermodynamic temperature scale) V2/V1 = T2/T1 = (273+40)/(273+20) = 1.068 6.8% increase in volume. 12

13. Summary • Thermal Equilibrium and Zeroth Law • Temperature and scales and conversions • Thermometric properties and thermometers • Ideal Gas Law • Kinetic Theory explains gas behavior in terms of Newton’s Laws of Motion. • /

15. 0

16. 0 The absolute temperature of a gas is most closely associated with its molecules average • Velocity • Speed • (Speed)2 • Momentum

17. 0 What happens to the pressure of an ideal gas going from state A to B? • Increases • Decreases • No change

18. 0

19. 0