Estimating oil molecule diameter

[Bolter]

Homework Statement

Working out an estimation of molecule's diameter

Relevant Equations

V = 4/3*pi*r^3

Can anyone help me in what assumptions I can make and how to justify them for when working out diameter of the molecule in part b) of this question? You can see the method that I have used in my workings but how would I explain it in words?

I obtained the diameter to be 0.13 nano metres which seems like a sensible length for a molecules diameter?

Thanks for any help! :)

 

[gneill]

How did you arrive at the radius of the cylinder being 0.4 (presumably meters)?

 

[Bolter]

How did you arrive at the radius of the cylinder being 0.4 (presumably meters)?

View attachment 254528

I made a silly mistake and used the diameter's length in metres and not the radius length. So it should have read 0.2m instead.

I have changed from 0.4 to 0.2 and get the thickness of d to be 0.521 nano metres now

 

[gneill]

Yes, that looks better!

 

[Bolter]

Yes, that looks better!

Ok so the only assumption that I have made in this problem is that the cylinder thickness is 1 molecule's diameter thick. How do I justify such an assumption?

 

[gneill]

Ok so the only assumption that I have made in this problem is that the cylinder thickness is 1 molecule's diameter thick. How do I justify such an assumption?

Perhaps look into surface tension.

 

[Bolter]

Perhaps look into surface tension.

Possibly.
I think I'll need to look into that more myself before I make my own justification as I'm a bit hazy over that. But thank you :)