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# A Level Chemistry Homework Watch

1. Hey I had my enrollment at college a few weeks ago and the homework is to calculate the size of an olive oil molecule and devise an experiment in a school lab or kitchen to work it out. It says to use this website for any information and I have no idea could someone please help? THANKS http://www.rsc.org/learn-chemistry/c...=1399160447243
2. What do you mean by size?
3. College.. Like AS level or degree level?
4. (Original post by :DD:D)
Hey I had my enrollment at college a few weeks ago and the homework is to calculate the size of an olive oil molecule and devise an experiment in a school lab or kitchen to work it out. It says to use this website for any information and I have no idea could someone please help? THANKS http://www.rsc.org/learn-chemistry/c...=1399160447243
Damn that's a pretty tough question for starting AS levels...

Find the density of olive oil is the first thing I'd do, and the molecular formula of an olive oil molecule.
5. (Original post by :DD:D)
Hey I had my enrollment at college a few weeks ago and the homework is to calculate the size of an olive oil molecule and devise an experiment in a school lab or kitchen to work it out. It says to use this website for any information and I have no idea could someone please help? THANKS http://www.rsc.org/learn-chemistry/c...=1399160447243
http://www.schoolphysics.co.uk/age16...rop/index.html
http://practicalphysics.org/estimati...-oil-film.html

From what I have found, you need to measure the radius of an oil droplet, r. From this you can calculate the volume of the oil droplet using V = 4/3 x πr3. Then, drop the oil droplet into a tray filled with water that has been lightly dusted. The oil will then spread out and form a large circle, and you should measure the maximum diameter of the circle to find the radius of the circle, R. The volume of the circle layer of oil is given by V = πR2 x h, where h is the thickness of the layer of oil.

Since the volume of the layer of oil is the same as the volume of the oil droplet, you can equate the volumes, hence 4/3 x πr3 = πR2 x h. Cancelling π gives 4/3 x r3 = R2 x h.

The thickness of the layer of oil can be no less than the size of an oil molecule, hence assuming that the oil forms a monomolecular layer on the surface of the water, the size of the oil molecule can be determined by rearranging the equation to find h, and plugging in the values of r and R.

Hence the size of an oil molecule, h = (4r3)/(3R2).

It is unlikely that the oil will form a monomolecular layer, hence the value of h will be the maximum possible size of the oil molecule.

(Original post by richpanda)
Damn that's a pretty tough question for starting AS levels...
I agree. After having done A level chemistry (AQA), I have never encountered anything like this and it is unlikely that you will either, unless this is on other exam boards. Although I guess the question is just supposed to get you thinking and just because something isn't necessarily on the syllabus, doesn't mean it isn't interesting and you shouldn't bother with it. If you enjoy your subjects it is always good to read around the subject, not just what is on the syllabus.
6. Have a look at Millikan's oil drop experiment. That should form the basis on what you're trying to find.

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