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Why Oil And Water Do Not Mix?

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Does Oil Dissolve In Water?

Every one of us will notice that the oil does not dissolve in water. You may have a question: does oil dissolve in water? Sometimes we may try to add oil to water and stir it continuously. But, it will stay as two distinct layers. This is the time for us to know the science behind why do oil and water not mix with each other. Check the entire article to know more information. 


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Why Do Oil And Water Not Mix?

We all know that every particle in the universe is made up of atoms, atoms are combined together to form molecules. If we need to mix two components, then the molecule of each substance should react with each other. So, the molecular structure of the oil and water is the main reason why oil and water do not mix. Usually, the molecules of oil and water do not mix with each other.  That can be noticed while washing the oily hands in simple water. While pouring oil in water it utilizes. The molecular density of the oil is comparatively high while comparing with water’s molecular density. So, it is difficult to break the bonding between the oil molecules. 

What Is Water? 

Water is a colourless, odourless, and tasteless transparent substance. The water has no calories and no organic materials. The chemical formula of water is H2O, which means, the water is made up of two hydrogen atoms and one oxygen atom. The hydrogen atoms are attached to the oxygen atoms at 104.45°. The water can be easily transferred to a solid, liquid or gaseous state by applying or removing heat from the water. Water plays an important role in determining the world economy because all the living organisms in the world are depending on water. The density of the water is 1,000 kg/m3 and the boiling point of the water is 100°C. 

What Is Oil? 

Oil is a nonpolar chemical substance and is one of the viscous liquids at ambient temperature. The oil can act as a hydrophobic and lipophilic liquid. This means, oil does not mix with water and it can easily dissolve with other oil substances. Usually, oil is a hydrocarbon liquid, which contains high carbon and hydrogen content. So, the surface of the oil is a flammable liquid. So, they are widely used as fuel for vehicles. Most of the oils will remain as a liquid at room temperature, but they are unsaturated lipids. So, they are greasy in nature. The oils can be obtained from natural resources or by breaking down fatty substances. They are also used for cooking food substances and acts as lubricants for vehicles. 

Why Oil Floats On Water? 

The molecules of the oil are bigger than the water molecules. So, they could not mix with each other easily. Also, the water molecules are polar substances, which means one point of the liquid is a positively charged particle and another point of the substance is a negatively charged particle. But the oil molecules are nonpolar substances, which means they do not have positive and negative charges. So, the oil and water molecules do not mix together. As the water molecules are made up of two hydrogen atoms and one oxygen atom they will stick together with the water molecules only. So, the polar molecules will dissolve only the polar solvents. Likewise, the nonpolar substances will dissolve the nonpolar solvents. As the oil is a nonpolar substance, the negatively charged electrons in the outer surface of the oil molecules will hold all the oil molecules together and create a layer. Even while stirring the water and oil mixture, they won’t combine together. They will eventually spread into different layers. 


It is possible to add an emulsifier to mix oil and water together with an external force and results to form an emulsion liquid. The emulsion is created with a stable mixture of water with droplets of oil spreading to the surface. The droplets of water or oil do not combine with each other. 

Experiment By Oil Mixing With Water 

While keeping the equal quantity of oil and water together in the same tube, the oil starts floating on the surface of the water. Because the density of the oil is lesser than the water. While adding a pinch of salt in a tube containing an equal quantity of the oil and water, The density of the salt is greater than the water, it will make the oil settle down at the bottom and salt will dissolve in water.  Once the salt is completely dissolved in water, the oil will start floating at the top of the water. 

Disadvantages Of Oil Not Mixing With Water 

  • While dispersing oil into the sea/ocean, it is spoiling the life of marine organisms. By inhibiting the respiration of the organisms. 

  • The oil in the water habitat will block the sunlight to enter the water. 

  • It will disturb the pH level of the water. 

This article explained, Why oil and water do not mix and the reason which prohibits Oil dissolve in water.  The complete science behind why oil floats on the water is given with examples in detail. 


FAQs on Why Oil And Water Do Not Mix?

1. Why oil does not dissolve in water?  

Usually, oil and water do not mix together. Oil will float on the surface of the water. This is only because the density of oil is lesser than the density of the water. But salt will dissolve in water because the density of salt is greater than the density of water. 

2. What happens when oil is mixed with water?

If you drop oil in water, it will float on the water. The water molecules attract each other, so the oil molecules get attached to the water molecules. Later, the oil and water molecules together will form two separate layers. As the water molecules are tightly packed they will sink at the bottom and leave oil molecules to settle at the top of the water molecules. 

3. What is it called when oil and water mix?

Any two liquids, which could not mix together easily is known as an emulsion. So, an emulsion is called a temporarily stable mixture of immiscible fluid. So, while oil is mixed with water it will be finely divided into very small droplets and form an emulsion liquid.