K.C.S.E Physics Q & A - MODEL 2017PP1QN16

K.C.S.E Physics Q & A - MODEL 2017PP1QN16

​(a) In an experiment to determine the size of an oil molecule, oil is placed on the surface of water after sprinkling lycopodium powder on it.
(i) State two reasons why oil is used. 
(ii) State the function of the lycopodium powder. 
(iii) State any two assumptions that are made in this experiment. 
(iv) Explain why the oil spreads on the surface of water.

(b) The following data was obtained from an experiment to determine the size of a palm oil molecule.
— Volume of 100 drops of palm oil = 15.0mm³
— Area of a patch from one drop of oil = 8.0 X 10⁴ mm²
Determine the size of a palm oil molecule.

answers

​(a) (i) Oil doesn’t mix with water. 
 Oil is less dense hence floats on the water surface. 
(ii) To show boundary of the oil patch clearly, for measurements to be taken. 
(iii)  The oil drops is a perfect sphere.
 The patch is monolayer.
 The patch is a perfect circIe
 Molecular diameter is uniform.
(iv)  The oil breaks the surface tension V making the patch to form a perfect circle.