This question on surface tension was very popular among the candidates although the part (a) of it was poorly attempted but part (b) was well attempted. Few candidates lost marks in part (b) for not using the correct action word (verb). Some candidates erroneously wrote ‘soap’ 'use soap’ ‘use detergent’ etc. This was vague.
The correct action word is ‘by adding* or by addition’
The expected answers are:
- Is the force per unit length acting in the surface at right angles to one side of a line
drawn in the surface of a liquid OR
The property of a liquid that makes it behave as if its surface is an elastic skin
- Two methods of reducing surface tension e.g by adding - detergent
- soap
- alcohol
- oil
- increasing the temperature
