A small drop of oil has a volume of 5x10^-8 m^3. When it is put on the surface of some clean water, it forms a circular film of 0.1 m^2 in...

area. What is the size of a molecule of oil? State any assumptions you make in your calculation.

### 1 Answer | Add Yours

Assumption: the circular film is one molecule thick (a monolayer).

The circular film can be treated as a cylinder with a very large cross-sectional area compared to its **height** which is the **same as the size of one molecule**. Imagine a million ping pong balls floating in a circular patch on a lake.

The volume of the film is the same as the original drop.

Volume of a cylinder, V = A x h (A = area of film, h = height)

Rearrange for h: h = V / A = (5 x 10^-8)/(0.1) **= 5 x 10^-7 m **

### Join to answer this question

Join a community of thousands of dedicated teachers and students.

Join eNotes