Observation

Candidates displayed vague knowledge about surface tension and its effect by their unthinkable submission. Few candidates were able to correctly list the two factors. Majority listed area of the surface as a factor to lose a mark. In the second part, many candidates mentioned boiling and use of chemicals as a means of making floating mosquito larvae sink and lost mark for it. Candidates performance was poor.

The expected answer

(a)     Surface tension depends on :
e.g  -  purity of liquid
-   temperature of liquid
-   nature/type of liquid
(b)      Mosquito larvae can be made to sink by the addition of any of:    
-   detergent/soap
-   alcohol
-   heat

-   camphor