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Physics Paper 2, MAy/June. 2009  
Questions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Main


General Comments
Weakness/Remedies
Strength











Question 3

Explain why mercury does not wet glass while water does.


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Observation

Good responses were given by many candidates.  Few fumbled due to their failure to relate cohesion and adhesion forces with molecules of mercury and glass.

The expected answers are:

Mercury does not wet glass because (force of) cohesion/attraction of mercury molecules is greater than (force of) adhesion/attraction between glass and mercury molecules.

Water wets glass because (force of) adhesion/attraction between glass and water molecules is greater than (force of) cohesion/attraction of water molecules.

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