Why Does Oil Float On Water? The Science Behind It

Oil Float On Water
Read Time:6 Minute, 21 Second

You may be wondering why does oil float on water? Most people believe that oil and water are natural enemies when they see them mixing together.

However, when it comes to why oil and water don’t mix and floating oil, these substances have some unique characteristics that make them stand out from the others.

In this article, we’ll look into why oil floats on top of water and why it doesn’t mix with water. Additionally, we’ll examine why a liquid’s density is crucial for this separation.

Oil floats on water because it is lighter than water. It would have sunk if it had been something heavier than water, like iron. The density of an object is a measurement of its mass per unit volume.

If you take a cubic centimeter (cc) of oil and a cubic centimeter (cc) of water, their masses are proportionally different; however, their volumes are identical. You can also explain this phenomenon in terms of buoyant force.

When oil is submerged in water, the buoyant force, which is equal to the weight of the water displaced by the oil, counteracts its weight. When oil is in water, its buoyancy force is much greater than its weight. As a result, it floats.

Weight Of Water

Water’s weight is influenced by temperature. One US gallon of water weighs 8.345 pounds (3.785 kg) at 17 degrees Celsius, but one Imperial gallon weighs 10.02 pounds (4.545 kg).
1 One Imperial gallon (g) weighs 16.6% more than one US gallon (gal).

The Density Of Water G/ML

Approximately 1 gram per milliliter is the density of water in g/ml, but this can vary depending on temperature or the presence of dissolved substances. Ice is less dense than liquid water that’s why ice cubes float on water.
A common unit of measurement for water’s density is grams per milliliter (1 g/ml) or 1 gram per cubic centimeter (1 g/cm3). The density of water on Earth at 4°C is 1000 kg/m3.

Why Don’t Oil And Water Mix?

The adage “like dissolves like” should be kept in mind when mixing liquids. However, water and oil are not the same. Polar molecules make up water. They are drawn to one another by the intermolecular force of hydrogen bonding, which is the bond created when one water molecule’s slightly negative oxygen side attracts another water molecule’s slightly positive hydrogen side.

However, because the oil molecules are hydrophobic, or afraid of water, they are non-polar and do not attract the water molecules as strongly. We can better understand it if we consider the idea of a dipole moment.

Dipole Moment

You can imagine a dipole as a magnet. It has a positively and negatively charged end analogous to the north and south poles of a magnet. The dipole moment, also referred to as the strength of the dipole, is the result of the difference in the magnitudes of the two charges and their separation from one another. To mix, the two liquids need to have comparable dipole moments.

Similar-strongness dipoles dissolve more quickly with one another than are dipoles with different-strongness. They don’t dissolve in each other because water and oil (like those that are hydrocarbon based) have very different dipole moments.

Oil Spill In The Ocean: Why Does It Float?

Oil spills in the ocean have been mentioned a few times. But why does the liquid keep rising to the surface of the water, never dissolving or blending in with it? Have you given it any thought?

As the saying goes, oil and water do not mix. Water always lies below the oil layer because it is denser and heavier than oil.

Actually, the main difference between oil and water molecules is that the former are nonpolar and the latter are polar.

Chemical analysis indicates that non-polar molecules actually repel one another and do not dissolve in polar solvents. This property can be cited as the reason why oil and water never mix.

Oil Float On Water

Properties Of Oil: Facts

  1. Both aquatic animals and sea life as a whole benefit from this component. They stay warm in the winter when they spend the majority of their time in the water thanks to the oil that coats their feathers and coats.
  2. Since oil weighs more than fresh water, it floats on the surface of salt water. You can spot this pattern using corn oil, cooking oil, crude oil, and other comparable oils.
  3. If you put ice in a container and fill it with oil, it will float. The reason for this is that ice is less dense than oil. It sinks to the bottom, though, as its density rises as it melts into the water.

The Heaviest Liquid—is That Water?

The short answer to this is “no.” Water is not the heaviest liquid. According to science, there are numerous other liquids in the world that are heavier than water. Around 1 g/ml is the density of water. The fact that water’s density varies with temperature and reaches its highest point at about 39.2 °F (4 °C) is what I find to be the most absurd aspect of the substance.

The heaviest liquid is mercury, not water. There are other liquids also there which are heavier than water. Glycerol and syrups are known to be heavier than water. Any of these added to water will cause it to sink to the bottom of the glass. Water is heavier than other liquids like oil and alcohol even though it may not be the heaviest liquid. These liquids float on the surface and don’t mix well. Water and oil do not mix and are incompatible. Whether water is the thinnest liquid or not has been documented, but it is undoubtedly thin in nature. Wax has an interesting fact. Wax floats on water but sinks in kerosene oil!

Which Fluid Has Greater Density Than Water?

One of the liquids that has a higher density than water is glycerol. The polar solvent water. Mass divided by volume equals density. Volume is inversely proportional to density in this situation, whereas mass is directly proportional. This means the bigger the mass, the bigger the density while the bigger the volume, the smaller the density. Therefore, if two objects have the same volume, the object with the higher mass will have a higher density.

Glycerol is one of the liquids that is heavier than water, but there are many other liquids that are as well, unlike oil. Corn syrup is one of those other liquids. Since corn syrup is heavier than water, it will sink if you add it to water. With a density of 450.6 oz/qt (13.5 g/ml) among all of these, mercury is regarded as the heaviest liquid. If you add something to water, it will sink if it is heavier and start floating if it is lighter. Water and oil don’t get along, and because oil has a lower density than water, it always floats on top of the water.


  • The answer to the question “Why does oil float on water?” is that oil floats on water because of its lower density than water.
  • Oil and water molecules do not mix with each other due to the polarity of water molecules and the non-polarity of oil molecules.
  • The volumetric mass of a liquid, expressed in cubic meters, is its density.
  • When oil is spilled in water, the buoyant force (upward force) is much greater than the weight of the oil, causing it to float.

Related Posts

Average Rating

5 Star
4 Star
3 Star
2 Star
1 Star

Leave a Reply

Your email address will not be published.

Pin It on Pinterest