Thermal conduction k where CV m is the

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Thermal conduction k= where CV, m is the molar heat capacity at constant volume.

Thermal conduction k= where CV, m is the molar heat capacity at constant volume. Because λ is inversely proportional to the molar concentration of the gas, thermal conductivity is independent of the concentration of gas, and hence independent of the gas pressure. One exception: at very low pressure, where the mean free path is larger than the size of the container.

 • J(x-component of momentum) = , η is the coefficient of viscosity.

• J(x-component of momentum) = , η is the coefficient of viscosity.

Viscosity • The viscosity is independent of the pressure. • Proportional to T 1/2

Viscosity • The viscosity is independent of the pressure. • Proportional to T 1/2

Measuring the viscosity • Poiseuille’s formula:

Measuring the viscosity • Poiseuille’s formula:

Calculations with Poiseuille’s formula • Example: In a poiseuille flow experiment to measure the

Calculations with Poiseuille’s formula • Example: In a poiseuille flow experiment to measure the viscosity of air at 298 K, the sample was allowed to flow through a tube of length 100 cm and internal diameter 1. 00 mm. The high-pressure end was at 765 Torr and the low-pressure end was at 760 Torr. The volume was measured at the latter pressure. In 100 s, 90. 2 cm 3 of air passed through the tube. • Solution: Reorganize Poseuille’s equation:

Molecular motion in liquids

Molecular motion in liquids

24. 5 Experimental results • Measuring techniques: NMR, ESR, inelastic neutron scattering, etc. •

24. 5 Experimental results • Measuring techniques: NMR, ESR, inelastic neutron scattering, etc. • Big molecules in viscous fluids typically rotate in a series of small (5 o. C) steps. • Small molecules in nonviscous fluid typically jump through about 1 radian (57 o. C). • For a molecule to move in liquid, it must acquire at least a minimum energy to escape from its neighbors. • The probability that a molecule has at least an energy Ea is proportional to e-Ea/RT. • Viscosity, η, is inversely proportional to the mobility of the particles, η∞ e. Ea/RT

Temperature dependence of the viscosity of water

Temperature dependence of the viscosity of water