DP Chemistry (last assessment 2024)

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Question 20N.3.hl.TZ0.4b(ii)

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Date November 2020 Marks available [Maximum mark: 3] Reference code 20N.3.hl.TZ0.4b(ii)
Level hl Paper 3 Time zone TZ0
Command term Explain Question number b(ii) Adapted from N/A
b(ii).
[Maximum mark: 3]
20N.3.hl.TZ0.4b(ii)

There has been significant growth in the use of carbon nanotubes, CNT.

(b(ii))

Explain the role of electrons in superconducting materials in terms of the Bardeen–Cooper–Schrieffer (BCS) theory.

[3]

Markscheme

Any three of:

passing electrons «slightly» deform lattice/displace positive ions/cations ✔

electrons couple/form Cooper pairs/condense with other electrons ✔

energy propagates along the lattice in wave-like manner/as phonons ✔

Cooper pair/electron condensate/pair of electrons moves through lattice freely
OR
phonons are «perfectly» elastic/cause no energy loss ✔

Examiners report

The role of electrons in superconducting materials in terms of the Bardeen-Cooper-Schrieffer (BCS) theory was very well understood and many scored all three marks. 

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