# Physical properties

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Physical properties
EGA108 / EG-279 ASSESSED SHEET 1
To be handed in via Blackboard by 5pm on Thurs Nov 8th. Show your workings in all cases – if you want to include hand-written workings, embed these as a scanned or photographed image. e = 1.6 x 10-19 C NA = 6.03 x 1023 me = 9.11 x 10-31 kg kB = 1.38 x 10-23 JK-1
By: darky- 712402
1 List two aspects of materials behaviour that the Drude model can explain.

The Drude model can explain the Thermal Conductivity in metals and Electrical Conductivity of metals.

List two aspects of materials behaviour that the Drude model can’t explain but the Quantum Free Electron model can.

Explains the effects of the temperature, impurities, and deformation on Electrical Conductivity in which the Drude Model can’t explain.

List two aspects of materials behaviour that the Drude and QFE models can’t explain but that Band Theory can.

The Band Theory can explain why the outer electrons become delocalised and the semi conductivity. [2 marks for each part]

2 Using the Drude model, for platinum, calculate the number of delocalised electrons per unit volume, their thermal velocity at 20°C and the average scattering length, given the following data:
Valency: 2 Density: 21450 kg/m3
Atomic mass: 195 Conductivity: 9.5 x 106 (m)-1
Temperature: 293K
Number of delocalised electrons per unit volume: n=(21450*1000*(6.02*1023)*2)/195 n=1.3244*1029 electrons/m3
Thermal Velocity at 293K:
Vthermal =
Vthermal =
Vthermal =115391.7586ms-1

Average scattering length: Rearranging the formula gives us this: = 2.945*10-10 m

[6 marks in total]

3 Qualitatively (so not using any formulae), explain:
a) How the Drude model predicts that the conductivity of metals decreases as the temperature increases.
The Drude Model considers the electrons to behave like gas particles, so they will have similar attributes to gas particles. Therefore Drude model predicts that the conductivity will be inversely

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