Detergents and Surface Tension

Bookmark added to your notes.
View Notes

There are some questions that we must have come across in our day-to-day lives. Have you ever encountered that raindrop does not adhere to any glass panel in a uniform order? What is the specialty of detergent or soap that it can wash our clothes much better than normal water?

Well, in this subject, we are going to study and analyze all kinds of behaviors regarding surface tension and detergents.

What is Surface Tension? 

It is defined as the attractive force which is applied to the molecules available on the surface of the liquid by the molecules underneath. This inclines to attract into the bulk of the liquid and influences the liquid to imagine the shape consisting of lowest surface area.

[Image will be Uploaded Soon]

Surface Tension of Soap Solution

Soap molecules consist of a long chain of hydrogen and carbon atoms. This is the infrastructure of atoms that enjoy inside water. The other terminal is easily connected with the soap molecule. The molecules of soap surround the water particle.

Surface tension of water breaks with the help of the detergent molecules attached to the water molecule at both its ends.

[Image will be Uploaded Soon]

The grease particle is moved apart and connected with soap molecules, to be accomplished by a water jet spray.

The two terminals of detergent molecules help to break the surface tension of water. This is called hydrophobic. The hydrophobic terminals of the detergent particle are being pushed up to the water surface in an attempt to draw out from the water molecule.

This phenomenon helps to weaken the hydrogen bonding of water molecules available at the surface. This destroys the surface tension of water.

[Image will be Uploaded Soon]

The soap molecule does not desire to convert into liquid form in a soap and water solution. The molecules which have found their path to the surface destroy their path between the molecules of surface water by raising the hydrophobic ends on the water surface. This phenomenon breaks the water molecules apart from each other.

Effect of Detergent on Surface Tension

The effect of detergent on surface tension brings a non-adhesive nature in water molecules. It does not stick to the surface of the glass.

It happens because of the cohesive force in the water-detergent molecule. The exact thing appears when it comes to washing clothes with water. Water can’t help much to clean the dirt. This is where we need detergent powder.

The mixture of detergent and water decreases water’s surface tension. We call detergents and shops as surfactants. The surfactants decrease the surface tension and increase the sticking capacity of the things.

Water in combination with detergent has the capability of strain through thin fibers of dirty clothes. The detergent solution spreads throughout clothes very easily than water.

This is the only reason why water can’t help along with the washing of clothes.

The surface tension of water on adding detergent to it.

When detergent is combined with water, it reduces its surface tension. The compounds which help to reduce water’s surface tension are known as surfactants.

In this whole phenomenon, the lowered surface tension area can be seen where the surfactant is combined with water. These surfactants can be illustrated as detergents, soaps, emulsifiers, foaming agents, and dispersants.

This word “surfactant” is the composite of a surface-active agent.

How Detergent Reduces the Surface Tension of Water?

As we have seen how detergent is acting in the water molecule, we can easily determine that it lowers the surface tension in the water. This phenomenon is caused because of surfactants that reduce the surface tension.  

What are the Factors Affecting Surface Tension?

These are the following reasons affecting surface tension


It is the prime factor that helps to reduce surface tension. The surfactants combine with a water molecule and lower its original surface tension.

Chemical additions

It changes the characteristics of surface tension. When some random chemical is mixed with a substance, it changes the surface tension. A surfactant in water is the best example of chemical addition.


It has a direct effect on surface tension. Oxidation is a natural phenomenon that appears when oxygen available in the atmosphere helps to lower the surface tension. The impurities that exist on the surface directly influence the surface tension.


This temperature factor initiates a decrease in surface tension. Though surface tension decreases, the molecules inside the solution have become operative, with the hike of temperature turning into zero.

Uses of Surface Tension in Real Life

Some real-life applications of the surface tension are:

  • It generates a high surface tension in water. The molecules are combined to create a film on the water surface.

  • This film, or the thin layer, is strong enough to embrace light objects like a blade or a pin made of tin.

  • Surface tension helps to form water drops without making it into a thin layer.

  • It also permits water to pass through roots, stems, thermometers, and in the blood vessels of our body. The pulling effect comes into action when one molecule moves up; it attracts the nearest one.

FAQ (Frequently Asked Questions)

Q1. Why is the Surface Tension of Water Lowered By Soap?

Ans: Soap molecules contain long chains of hydrogen as well as carbon atoms that differentiate the water molecules from each other by decreasing their surface tension. As a result, there is a rise in the distance between water molecules.

Q2. What is the Portrayal of Detergent?

Ans: It helps to reduce the surface tension of water. Detergent acts as a surface-active agent or surfactant for short. They act with a water molecule to create a gap between them, which lowers the surface tension among them.

Q3. Mention Some Reaches, Which Helps to Increase the Surface Tension of Water?

Ans: The availability of impurities in the surface water reduces its surface tension. When the highly soluble impurities are added to water molecules, it pushes to the surface tension of water.

Q4. What Happens When Water will Lose its Surface Tension?

Ans: If there is no surface tension, the water molecules will evaporate immediately. This is a condition which only arises when there will be no attractive forces among the molecules of the fluid.