TRANSPORT PROPERTIES

1. TRANSPORT PROPERTIES Ch 30 Quantity Gradiant Laws Temperature Heat HOT - + Electrons Potential - - - - - - - - - - - - - - - Mass Pressure -- - - - - - - - - - - - - - - - - - -- Mass Concentration Momentum Velocity Flux = Jz = amount transported across unit area per s

2. Flux- Gases 1 N C 6 Transport is by discrete carriers and each carrier transports a finite amount In 1 second 1/6th of all molecules present in the box of dimensions will pass through the shaded area C z # of molecules traveling along ‘Z’ = # of molecules crossing the face in one second = If each carrier transports quantity ‘q’

3. T 2 HOT Z T 1 COLD T T1 T2 Potential Gradient in the System Z

4. Thermal Conductivity of an Ideal Gas – Part 1 Z  Z+ C { Z  T 1 3  N C T Z -  B 1  Z 6 2 {   Z- [ ] A  T 1 3 N C T Z +   k + From ‘A’ to‘B’ = 1  Z 6 2  T 1 3 N C [ ]  Z 6 2  k From ‘C’ to ‘B’ = + [ ] - 2 =  k -  Since heat is a manifestation of K.E. and is transported via collisions between carriers, we shall consider gas collisions & mean free path ‘.’

5. Thermal Conductivity of an Ideal Gas – Part 2 [ ] - 2  k -  Net Flux = = = = -   T  T 1 3 N C  Z  Z 6 2

6. Mean free path ‘’  Average distance traveled in 1s = If ‘Z’, = number collisions per s, = C Consider a cylinder of radius,  , length In 1s, molecule will travel from one end to the other # collisions made by one molecule per s = But average relative velocity = A = 0 =2C =sqr2C Collision number = Mean free path = Relative Velocity

7. Diffusion:substances diffuse from a high concentration region to a low concentration region. Z Nz+ Nz Nz- x Net Flow Homework: Poizulle Formula & Viscosimeter