Measuring the size of a molecule

In summary, the conversation was about using the oil drop experiment to determine the size of a molecule. However, the speaker was having trouble getting a perfect circle and was using talcum powder instead of lycopodium powder. The other person suggested making an estimate of the area of the oil patch using a grid of square cm on a transparency and taking into account the minimum and maximum possible area for a more accurate result.
  • #1
ecy5maa
30
0
Hi,

Homework Statement


I am trying to determine the size of a molecule..by doing the oil drop experiment where we drop a tiny droplet of oil on water covered with a thin layer of powder...and then make calculations based on the diameter of the circle... the droplet forms in oil.

The Attempt at a Solution


However, the oil droplet for me is not making a circle..rather is spreading out irregularly. How can I fix this.

Everything i have used is according to this site:
Code:
[PLAIN]http://www.practicalphysics.org/go/Experiment_633.html[/PLAIN] [Broken]
but i have used talcum powder instead of lycopodeum powder
 
Last edited by a moderator:
Physics news on Phys.org
  • #2
I never saw a circular oil patch when my students did this experiment.
An irregular size is not much of a problem because the whole experiment is more of an estimate than a measurement. Just estimate the area of the oil patch. You can make a very good estimate if you make a grid of square cm on a transparency and hold it over the patch. A nice touch is to estimate the minimum and maximum possible area. Use a number midway between these as your "best" value, but also work out the size of a molecule using the low and the high. Then you will have not only a "best" answer but a known accuracy range.
 

1. How is the size of a molecule measured?

The size of a molecule is typically measured using a technique called X-ray crystallography. This involves shining X-rays onto a crystallized form of the molecule, which causes the X-rays to diffract and create a pattern that can be used to determine the molecule's size and shape.

2. Can molecules of different sizes be measured using the same method?

Yes, X-ray crystallography can be used to measure the size of a wide range of molecules, from small molecules like water to large biomolecules like proteins. However, the technique may need to be adjusted depending on the size and complexity of the molecule being measured.

3. Is there a limit to the smallest molecule that can be measured?

Yes, there is a limit to the smallest molecule that can be measured using X-ray crystallography. This is because the technique requires a crystallized form of the molecule, which may not be possible for very small molecules. In these cases, other techniques such as electron microscopy or nuclear magnetic resonance (NMR) spectroscopy may be used.

4. How is the size of a molecule related to its properties?

The size of a molecule can greatly affect its properties, such as solubility, melting point, and reactivity. Generally, smaller molecules have lower melting points and are more reactive, while larger molecules tend to have higher melting points and are less reactive. This is due to the different intermolecular forces that come into play with different molecule sizes.

5. Can the size of a molecule change?

Yes, the size of a molecule can change in certain circumstances. For example, molecules can undergo chemical reactions that break or form bonds, changing their size and shape. Additionally, environmental factors such as temperature and pressure can also affect the size of a molecule. However, the basic size and shape of a molecule is determined by its chemical structure and is usually consistent under normal conditions.

Similar threads

  • Introductory Physics Homework Help
Replies
5
Views
21K
  • High Energy, Nuclear, Particle Physics
Replies
3
Views
1K
Replies
15
Views
1K
Replies
1
Views
3K
  • Introductory Physics Homework Help
Replies
2
Views
1K
  • Atomic and Condensed Matter
Replies
1
Views
1K
  • General Math
Replies
4
Views
1K
  • Introductory Physics Homework Help
Replies
6
Views
6K
Replies
5
Views
754
  • Introductory Physics Homework Help
Replies
14
Views
2K
Back
Top