Why Does Oil Float Above Water?

[gunblaze]

Oil Floating above water...?

Someone, please first answer this qn...
Is oil denser than water?

If yes, pls proceed...

When an oil spill occurs at sea, why would the oil float above the water?
If oil is denser than water, wouldn't oil be sinking to the bottom of the sea?
Could anyone pls offer an explanation to this qn.Thx

 

[dav2008]

Oil is less dense than water

 

[gunblaze]

oh...ok.Thx

 

[Moonbear]

Oil is less dense than water

Here is a list of densities of various liquids. http://www.simetric.co.uk/si_liquids.htm

 

[brewnog]

Oil is usually more viscous (not dense) than water, perhaps this is the source of your confusion.

 

[Integral]

Oil is usually more viscous (not dense) than water, perhaps this is the source of your confusion.

Humm.. viscousity has nothing to do with floating, density has everything to do with floating. Oil floats on water, therefore oil is less dense then water.

 

[russ_watters]

Humm.. viscousity has nothing to do with floating, density has everything to do with floating. Oil floats on water, therefore oil is less dense then water.

I think what Brewdog was referring to is the fact that the words "light" and "heavy" are often associated with the viscosity of oil. This could lead to confusion: http://www.lloydminsterheavyoil.com/whatislaunch.htm

What is Heavy Oil?

Heavy oil is a type of crude oil which is very viscous...

 

[arildno]

A denser liquid might float atop a less dense one if a sufficient surface tension developed at the interface layer (think of a needle made of metal floating atop water).
An oil, is however, less dense than water.

 

[Gara]

I heard if you boil water and let it cool down again, it removes a lot of oxygen in the water, thus making oil sink, instead of floating.

So maybe oil is denser than pure water, (H2O, nothing else) but not tap water?

 

[dav2008]

I heard if you boil water and let it cool down again, it removes a lot of oxygen in the water, thus making oil sink, instead of floating.

So maybe oil is denser than pure water, (H2O, nothing else) but not tap water?

I'm not sure to what extent your method would work but if you remove all of the dissolved air out of water it would make the water more dense so materials would have a higher tendency to float.

If you look at the chart that moonbear posted, every single item that's listed as an "oil" has a lower density than water.

 

[shikobe]

ummmm it has been 6 years later and i don't know if my response will mean anything to the people but i thought i would put it here anyway...part of your understanding lies in chemistry. Oil is composed of long chain hydrocarbon molecules so you would think it is more dense than water in that sense, but water is a polar molecule and will form hydrogen bonding with surrounding water molecules and hence, will be more closely packed giving a greater density since p=m/V. For oil on the other hand, it is a non-polar molecule and hence the only intermolecular forces holding the oil together are weak dispersion forces and hence the molecules of oil will want to be apart from each other as this is more 'energetically favourable', and hence oil is not packed tightly could be considered 'looser' and so appears less 'dense'.
Therefore the Force of gravity would act accordingly on the 'heavier' substance being water in this case, so oil is seen floating on top.

 

[pallidin]

Huh... never thought about it, but great explanations.
I must admit that I was under the impression that most liquids were heavier than water. Learn something new everyday!

Edit: perhaps it WOULD be correct to say that 1 fluid ounce of oil IS heavier than 1 fluid ounce of water.
But, the above post by shikobe explains how it can be different in a complex environment(polar/non-polar)
Hope I got that right.

 

[russ_watters]

Edit: perhaps it WOULD be correct to say that 1 fluid ounce of oil IS heavier than 1 fluid ounce of water.

Um...no, that's exactly the issue that was being discussed!

 

[sophiecentaur]

If you are talking about crude oil (the sort that you get in large spills), then the density and actual composition varies greatly, according to where it was extracted. I was listening to the radio, only today, aamof, and the Mexican Gulf spill has resulted in floating oil patches and large volumes of more dense oil sitting on the sea bed. The different fractions have clearly separated out. I wonder whether this was due to the action of bacteria - it couldn't have been the normal fractional distillation process as it never got hot enough.

 

[Andy Resnick]

Someone, please first answer this qn...
Is oil denser than water?

What kind of oil? What temperature and pressure?

If yes, pls proceed...

When an oil spill occurs at sea, why would the oil float above the water?
If oil is denser than water, wouldn't oil be sinking to the bottom of the sea?
Could anyone pls offer an explanation to this qn.Thx

At depth, crude oil can be denser than water- that is why the Deepwater Horizon spill was generally confined.to underwater plumes.

 

[sophiecentaur]

Oh yes - I see that water has about double the modulus of oil(s) so, unless it is brought to the surface by stirring, oil will tend to stay at great depths.

 

[pallidin]

Um...no, that's exactly the issue that was being discussed!

OK, let me correct that.
I am under the assumption(perhaps incorrect) that a 16oz glass filled with oil is physically heavier than a 16oz glass filled with water.
What do you say?

 

[russ_watters]

No! If it were, that would mean it was more dense. Oil is less dense than water. That's what "density" means!

 

[pallidin]

OK. Good enough for me. Thanks for clarifying.

 

[pallidin]

After some research I found this:

1 gallon of water weighs approx. 8.35 pounds.
Source: http://wiki.answers.com/Q/How_much_does_one_gallon_of_water_weigh

1 gallon of oil weighs approx. 6-8 pounds depending on density.
Source: http://wiki.answers.com/Q/How_much_does_one_gallon_of_oil_weigh

You guys are right. Not sure how I felt that something "thicker" should weigh more.
Oh well, I learn something new each day.
Cheers!

 

[cmendez79]

Can someone answer my question: if I have 10 ml of vegetable oil over 5 ml of water, will the oil still float over the water or will the order be reversed?

 

[Drakkith]

Can someone answer my question: if I have 10 ml of vegetable oil over 5 ml of water, will the oil still float over the water or will the order be reversed?

When I occasionally get water in the gas take of my lawn mower, the water sinks to the bottom. There would be a small layer of water underneath a large layer of oil.

 

[sophiecentaur]

After some research I found this:

1 gallon of water weighs approx. 8.35 pounds.
Source: http://wiki.answers.com/Q/How_much_does_one_gallon_of_water_weigh

1 gallon of oil weighs approx. 6-8 pounds depending on density.
Source: http://wiki.answers.com/Q/How_much_does_one_gallon_of_oil_weigh

You guys are right. Not sure how I felt that something "thicker" should weigh more.
Oh well, I learn something new each day.
Cheers!

The ultimate in 'thickness' would be 'solid? Manu solids are less dense than water and will float. 'Thickness' means viscosity usually - and is not 'density'.

Floating or sinking depends entirely on relative density.