What is Cohesion and Adhesion?
Many aspects explain various things on adhesion and cohesion, meaning and examples, which we observe in our daily life. Although, at times, we miss to focus on these little things, and these help us to keep our lives going on earth. The adhesion and cohesion forces are one of both phenomena. Although they sound to be similar, they are completely known to occur in different terms.
Surface tension is one of the important physical properties of water that describes the relationship between adhesion and cohesion.
Coming to the definitions, the tendency of either two or more different molecules to bond with each other is called Adhesion. In contrast, the attraction force between the same molecules is referred to as Cohesion.
About Adhesion and Cohesion
Adhesion forces can be one of the electrostatic forces' results exerted on various substances. Simultaneously, the cohesive forces are associated with the Van der Waals forces and hydrogen bonding that cause liquids like water to withstand the separation.
When a glass surface is poured with water, the forces of both adhesive, cohesive act on the water's surface. Also, a strong adhesive force tends the liquid to spread over the surface; on the other side, a strong, cohesive force is responsible for forming water droplets on the water surface.
Both the adhesion and cohesion forces vary in their strengths. For example, if the cohesion forces between water molecules are stronger compared to the adhesion forces between them, then the individual molecules present in them will attract towards each other hence resulting in settling. If the adhesion forces of the water surfaces are stronger than the water molecules' cohesion forces, the water tends to disperse then.
Difference Between Cohesion and Adhesion
Let us discuss the adhesion and cohesion difference.
Adhesion and cohesion are attraction forces, exist between different and the same molecules, respectively. Though they sound to be similar, they differ from each other. Let us come to know how cohesion differs from adhesion, and the primary differences between them are tabulated below:
Relationship and the Meaning of Cohesion and Adhesion
In general, cohesion and adhesion forces exist together; you can find these respective forces in various activities and processes. Consider the example, meniscus, which is a liquid surface curvature stored in a tube or container, is caused by both adhesion and cohesion. The attraction force between the edges of liquid and the container wall is called adhesion. The attraction force between the water molecules, which makes the liquid surface curved in the middle, is given cohesion.
Also, the meniscus shape is decided by these forces. If the cohesion force, which exists between the liquid molecules, is more than that of adhesion force existing between the liquid and the tube's inner surface, the meniscus shape will be convex. For example, mercury, filled in a glass tube. Similarly, if adhesion is more than that of cohesion, the meniscus will be concave. For example, water, filled in a glass tube. The surface will be horizontal if the cohesion is equal to adhesion.
Let us suppose you spill some water on a surface. If the adhesive force is strong, then the water will get absorbed soon by the surface, and also it will go wet. Whereas, if the cohesive force is strong, there will be more attraction between the water molecules than between the surface and water molecules. So, the surface absorbs less water.
Differences Cohesion vs. Adhesion
Based on the given information above, a few key differences between cohesion vs adhesion are listed.
FAQs on Difference Between Adhesion and Cohesion for JEE Main 2024
1. How is surface tension related to cohesive forces?
Surface tension is the result seen due to the cohesive forces that arise between two adjacent molecules. The molecules that are present in the liquid tend to be pulled equally from all the directions by the molecules that are near the one that is being pulled. But the surface molecules have no force from all sides. Instead, the forces are only pulling it inwards.
Due to this pull, water molecules tend to shrink to a surface that consists of the minimum area, which is a sphere. Hence it is seen that when water is being dropped drop by drop you see a spherical shape. While due to it is seen that the water molecules bead together on wax paper because surface tension tends to be greater than adhesive forces.
2. Is there a relationship between cohesion and adhesion?
Both cohesion and adhesion are highly related to each other. The two terms are used together to explain a particular effect. For example, the meniscus is formed due to both adhesion and cohesion. The curvature on a liquid surface that is present in a container is said to be the Meniscus. The edges of the wall that are in touch with the wall of the container are held at an upper level with the help of adhesion forces. The water molecules are hence due to the attraction force or cohesion forces, curved in nature.
3. What is capillary action and how is it related to cohesive and adhesive forces?
One of the most important concepts that have the application of adhesive and cohesive forces, capillary action has one of the most important applications being made. It is related to the relative strength of both cohesive and adhesive forces. The tendency of a liquid to be either raised or lowered in a narrow tube is called capillary action. It is seen that the capillary tube is placed vertically into a liquid, then the action wither raises or suppresses the liquid that is present inside the capillary tube.
The actual effect depends on the contact angle present between the wall of the tube and the liquid. If the angle is less than 90 degrees, then the fluid will be raised in the tube while if the angle is greater than 90 degrees, then the liquid present will be lowered.
4. Why are cohesive and adhesive forces important in life?
These two forces i.e., the cohesive and adhesive forces tend to play an important role in a lot of water-based processes in biology. This includes the processes such as passing of the water up to the treetops. This allows all the parts of the tree to get the water that they require for its functioning. This effect is also important in the drainage of tears from the corner of the eyes. Another simple example to understand the topic is to check the cohesion action that comes from the water strider which is an insect that relies on the surface tension to stay floating on water.
5. Mention any application of Adhesive and Cohesive Forces in daily life?
There is much difference between cohesive and adhesive force. When a fly walks on a vertical glass piece, the adhesive forces between the glass and its tarsal pads become sufficient to resist both the tendency to slide downward and the tendency to fall away from the glass surface.
The behavior of water molecules is a known example of cohesion. Every water molecule can result in the formation of four hydrogen bonds with their neighbor molecules. The strong attraction present between the molecules makes them "sticky" or draws them together.
Because the water molecules are more strongly attracted to each other to that of other molecules, they form droplets on the surfaces. For example, dew drops, form a dome when filling a container before it is spilling over the sides. The surface tension formed by cohesion allows it for the light objects to float on water with no sinking. For example, such as water striders walking on water.
6. How do the Adhesion and Cohesion processes work in plants?
The process works similarly in plants as anywhere else. Through xylem, both are important processes in the cohesion-tension theory of water movement. Xylem cells fall when working, and water molecules adhere to their cell walls. In these narrow tubes, adhesion leads to a capillary movement of the water. Also, up the xylem, there is a certain amount of root pressure forcing the water. However, the water does not climb far in the tubes. The cohesion force among the water molecules makes the tube of water a complete stand essentially from the leaves to the roots.
