Question regarding bonding in liquid.

[walker]

In an experiment related to bonding in liquid I was required to stir three liquids: Water, Paint Thinner, and Vegetable oil. Thereby creating a vortex in each liquid and recording the depth of the vortex plus the time the vortex took to disappear. My results where that water produced the deepest vortex as well as took the longest for the vortex to disappear.

Is this due to the stronger intermolecular bond in Hydrogen bonds?

 

[Gokul43201]

Most oils have stronger intermolecular bonding than water. Remember, vegetable oils boil at about 300C while water boils only at 100C.

What is the paint thinner made of ? Can you read the primary composition off the label ? Is it acetone based or does it have some long chain hydrocarbons ?

 

[Moonbear]

When I think of paint thinner, I think of turpentine, not acetone. So, I'd assume it contains long chain hydrocarbons. If you don't have a label to check, your nose will know...did it smell like nailpolish remover (acetone) or a petroleum product (turpentine)? Both are volatile enough that if you were creating a vortex, you probably would have noticed the odor, even if trying to work in a hood. :yuck:

 

[Gokul43201]

I guess it's probably turpentine then. (I think I've used a conductive paint that used an acetone thinner or solvent, but I may be wrong).

So, the thinner and the vegetable oil are more viscous due to greater intermolecular bonding. And it's harder to sustain a velocity gradient in a more viscous fluid. From that, you can explain both effects.

 

[walker]

http://michael_walker.shackspace.com/question.jpg

I've included the exact excerpt from my workbook.

From that we can see that the paint thinner is made up of methyl benzene (C6H5CH2) (toluene), is non-polar and is an example of van der Waals bonding.

The vegetable oil contains oleic acid (C17H33COOH) and is slightly polar which would be an example of dipole bonding.

And the water of course is an example of hydrogen bonding.

I'm still a little confused. You say that the viscous of the oil and paint thinner is due to greater molecular bonding. From what I've read, I was under the assumption that hydrogen bonds were actually the strongest of the three intermolecular forces (hydrogen, van der waals, dipole). That dipole were the weakest and that van der waals were dependent on the number of electrons within the molecule.

With all that being said. From my experiment I found the water to provide the greatest and longest vortex, the paint thinner to provide a slightly less vortex in terms of depth and time and the oil did not create a vortex at all.

So if the oil is made up of polar molecules meaning that the bonds between them are weak, wouldn't that mean that they would not conform to a vortex? The water molecules having the greatest amount of force between them they would conform to a vortex for a greater amount of time? The paint thinner being being non-polar and its force of van der waals bonding being the result of the shape and number of electrons would make it have a slight vortex yet not as long or as deep as water?

Like if you were to take a magnet and swirl it around in a bowl of other magnets the magnets will attract to each other and eventually you'll have this long chain of magnets making up a swirl... i hope that makes sense? is that what is happening with the water molecules? they're forming a vortex because I am swirling them around and they're trying to stay attached to each other?

 

[Gokul43201]

You could be right. I'll have to think about this a little more, but it seems that the stronger bonding in the case of water helps transfer momentum from the stirrer to the liquid better than oil or thinner. I think the faster the liquid swirls, the deeper will be the vortex. Viscosity should also play a role (and one would expect this to be directly related to the intermolecular bonding), but it may only be a second order effect. I'm not sure if the greater viscosity of oil comes from actually stronger bonding (the molecules are pretty long, so the bonding may end up being fairly strong) or only due to geometric factors (the ability of the molecular chains to interlock.)

       /\/\/\/\/\/\/\-COOH
HOOC-/\/\/\/\/\/\/\/\

But toluene is less viscous than water so clearly, it's not the viscosity that's the determining factor.

 

[hewgsad032]

I am doing the same experiment, but I got different results. Paint Thinner produced the deepest vortex and took the longest time to disappear. Water and Paint Thinner were very similar, but Vegetable Oil took the least time to go away, and made the smallest vortex.
One of the questions is: Why is water so much differentfrom the other substances in time and depth of vortex. But in my experiment it wasn't much differnt from Paint thinner. Did I do something wrong?

 

[alxm]

Just to clarify what was said above: Hydrogen bonds are indeed the stronger bond.
Oils are just much larger molecules, so their *total* intermolecular bonding energy is greater than that of water.