Adhesion and Cohesion Difference - Definitions, Relationship, FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 04:58 PM IST

In our daily lives, we see evidence of adhesiveness and cohesiveness in many facets of our lives. One of the common phenomena in adhesion and cohesion is force. Despite the fact that they have a similar sounding name, these things are commonly referred to by different names. The link between adhesion and cohesion can be described using surface tension, which is an important water property. As for the definitions, adhesion is the propensity of two or more molecules to form a chemical bond. As opposed to this, Cohesion refers to the force that draws similar molecules together.

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Cohesive forces
Adhesive forces
Relationship between cohesion and adhesion
Difference between adhesion and cohesion:

Cohesive forces

Hydrogen bonds and van der Waals forces are examples of intermolecular forces that contribute to the bulk feature of liquids, which is their inability to separate. These attraction forces exist specifically between molecules of the same material. For example, rain falls in droplets rather than a fine mist because water has a high degree of cohesion, which binds the molecules of water together securely to create droplets. Due to the molecules' hatred of their environment, this force tends to bring liquid molecules together, resulting in huge clusters.

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Adhesive forces

The force of attraction between different substances/objects is referred to as the term "adhesive forces". It includes mechanical forces (sticking together) and electrostatic forces (attraction due to opposing charges). Adhesion occurs when a liquid wetting agent adheres to the surface it is resting on. When water is spilled on a clean piece of glass, it spreads out and leaves behind a thin, even film on the surface. The reason for this is adhesive force. Water molecules are pulled out of the spherical shape due to the adhesive forces between water and glass and hold them against the glass's surface, as a result, the attraction between like molecules is avoided.

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Adhesive forces

Relationship between cohesion and adhesion

Cohesion and adhesion forces can be found in a variety of activities and processes. As an illustration, consider the meniscus, which is a Both adhesion and cohesion are to blame for liquid surface curvature when kept in a tube or container. In physics, adhesion is the force that pulls liquid against the container wall at its edges. Cohesion is created by the attraction force between water molecules, which causes the liquid's surface to bend in the middle.

The form of the meniscus is also determined by these forces. The meniscus will have a convex form if the adhesion force between the liquid and the inner tube surface is lesser than the cohesion force between the liquid molecules. As an illustration, consider mercury, which is housed in a transparent tube. Similarly, a concave meniscus will result if adhesion is greater than cohesion. For instance, water in a glass tube.

Surface will be parallel when adhesion and cohesion are the same. Assume you've just dropped some water on something. Unless the surface has a high adhesive force, water will run off and become soaked into the fabric. If the cohesive force is strong, water molecules will be more attracted to one another than surface molecules are to one another. As a result, water is absorbed at a slower rate on the surface of the water.

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The macroscopic effects of adhesive and cohesive forces

A liquid's form is defined by the strength of the cohesive and adhesive forces operating on it when it's applied to a smooth surface (and whether or not it will wet the surface).For a given liquid and surface combination, more adhesive forces cause the liquid to sink and saturate the surface beneath it; this is called evaporation. However, if the cohesive forces within the liquid are stronger, the liquid will be able to resist the adhesion and keep its spherical shape, causing it to bead on the surface.

Meniscus is the curvature of a liquid's surface inside a container, like a graduated cylinder.. Be that as it may, we must first understand the adhesive forces acting on surface tension in order to describe why some liquids have a concave up meniscus although others have a concave down meniscus. Water, for example, is a polar molecule with a partial positive charge and partial negative charge on the hydrogens and the oxygen respectively.

As a result, in liquid water, each molecule's partial positive charge attracts the adjacent molecule's partial negative charge. Cohesive forces in water originate here. Because the water molecules are being pulled and pushed equally in all directions, there is no net force on them. As a result, the molecules on the liquid's surface have a net downward pull because they lack upward pushing forces.

The solution lies in the interaction of water molecules' adhesive forces with the container's surface. Liquid convects downward to lessen contact with the wall's surface when its cohesive force is greater than its adhesive force on the wall. When the liquid's adhesive force to the wall exceeds its cohesive force, upward concavity is observed as the liquid is more attracted to the wall than its neighbors.

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Difference between adhesion and cohesion:

These two terms refer to forces of attraction that exist between separate molecules and inside the same molecule. Despite the fact that they sound similar, they aren't the same.

Adhesion occurs when two dissimilar molecules or substances come together and stick to one another. A cohesion force is generated when two comparable molecules or substances are attracted by the force of attraction.
Water molecules are attracted to the xylem vessel walls because of adhesion. Within the water molecules, cohesion force is rampant.
The adhesion effects include meniscus and capillary action, as well as (the curved liquid surface in a cylinder). Cohesion has effects on the meniscus, capillary action, and surface tension.
Mechanical or electrical forces generate adhesion between two different substance types. Van der Waals forces and hydrogen bonding cause cohesion.
The liquid can spread all over the surface due to any of the high adhesion forces that are in work there. Water droplets develop on any surface due to a strong cohesive force.
Molecules are drawn to one another by electrostatic attraction. Molecules with similar properties tend to group together.
A liquid's surface tension, water droplets, and capillary action are all caused by surface tension. It's because of the adhesion that a liquid like paint, glue, and cement spreads over a hard surface.

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Frequently Asked Questions (FAQs)

1. Do you have any examples of how Adhesive and Cohesive Forces are used in your everyday life?

Cohesive and adhesive forces are vastly different in nature. When a fly walks on a vertical piece of glass, the adhesive forces generated in between the glass and its tarsal pad of insect become adequate to resist both the tendency to slide down and the tendency to tumble away from the glass surface.Water molecules' behaviour is a well-known example of cohesion. Four hydrogen bonds can be formed between any two adjacent water molecules. Because of the tremendous affinity between the molecules, they become "sticky" and cling together. Droplets occur on surfaces because water molecules are more strongly attracted to one another than other molecules are. When dew drops fill a container, they form a dome before overflowing out the sides. The surface tension created by cohesiveness is what allows light items to float on water without sinking. Water striders, for instance, are creatures that can traverse water.

2. what is cohesive force?

Cohesion or cohesive force is generated when two comparable molecules or substances are attracted by the force of attraction.

3. What is adhesion?

Adhesion occurs when two dissimilar molecules or substances come together and stick to one another.

4. What role do adhesion and cohesion play in plants?

In plants, the process is the same as it is everywhere else. The cohesion-tension theory of water movement attributes both of these processes to xylem, which plays a key role in them. When the xylem works, the cells fall and the water molecules stick to the cell walls. Adhesion causes water to move capillary in these little tubes. There is also root pressure pushing water up the xylem. The water does not, however, go very high in the tubes. As a result of the molecular cohesion force, the water tube stands essentially straight up from the leaves to the roots.

5. What is the difference between adhesion and cohesion, and what are some examples of each?

Adhesion happens when two distinct substances come into contact. Adhesive force example: water molecules that stick to the beaker's plastic surface adhere more tightly around the rim. Cohesion occurs when molecules are attracted to one another and form a bond. This causes the molecules to adhere together. Cohesive force example: Rain falling as droplets.

6. What are the advantages of adhesion and cohesiveness in terms of living?

Capillary action is a mechanism in which cohesion and adhesion are crucial in human health. Water may move freely throughout a plant because of the way it adheres to vessels inside the plant. When the water is held together by cohesion, it is able to be drawn up into the plant against gravity.

7. What is adhesion in chemistry?

Adhesion is the attraction between molecules of different substances. It's the force that causes water to stick to glass or paint to adhere to a wall. Adhesion occurs due to intermolecular forces between unlike molecules.

8. How do adhesive forces affect the shape of liquid droplets on surfaces?

Adhesive forces between a liquid and a surface influence the shape of droplets. Strong adhesion causes droplets to spread out and have a lower contact angle with the surface. Weak adhesion results in more spherical droplets with higher contact angles.

9. Can you explain the concept of work of adhesion?

The work of adhesion is the energy required to separate two different substances at their interface. It's a measure of the strength of adhesive forces between the substances. Higher work of adhesion indicates stronger adhesion between the materials.

10. What is the relationship between adhesion and adsorption?

Adhesion and adsorption are related concepts. Adsorption is a specific type of adhesion where molecules, atoms, or ions from a gas or liquid adhere to a solid surface. The strength of adhesive forces determines the extent of adsorption.

11. How do adhesion and cohesion affect the process of distillation?

In distillation, cohesion keeps the liquid molecules together as they vaporize and condense. Adhesion affects how the condensed liquid interacts with the condenser surface, influencing the efficiency of the process and the purity of the distillate.

12. What causes surface tension in liquids?

Surface tension is caused by cohesive forces between liquid molecules at the surface. These molecules are pulled inward by other molecules deeper inside the liquid, creating a "skin-like" effect on the surface.

13. Why do some insects can walk on water?

Some insects can walk on water due to surface tension, which is a result of strong cohesive forces between water molecules. The insect's weight is distributed over a large area by its legs, allowing it to be supported by the "skin" created by surface tension.

14. How do detergents reduce surface tension?

Detergents reduce surface tension by weakening the cohesive forces between water molecules at the surface. They do this by inserting themselves between water molecules, disrupting the hydrogen bonding network.

15. What is the role of cohesion in plant transpiration?

Cohesion is crucial in plant transpiration. It allows water molecules to form continuous columns in the xylem, enabling water to be pulled up from the roots to the leaves against gravity. This phenomenon is known as cohesion-tension theory.

16. What is the difference between adhesive and cohesive failure?

Adhesive failure occurs when the bond between two different materials breaks at their interface. Cohesive failure happens when a material breaks within itself. For example, if glue separates from wood, it's adhesive failure; if the glue breaks internally, it's cohesive failure.

17. How does cohesion differ from adhesion?

Cohesion is the attraction between molecules of the same substance, while adhesion is between different substances. For example, water droplets form due to cohesion, but water sticking to a leaf is due to adhesion.

18. Why does mercury not wet glass surfaces?

Mercury doesn't wet glass surfaces because the cohesive forces between mercury atoms are stronger than the adhesive forces between mercury and glass. This results in mercury forming distinct droplets on glass rather than spreading out.

19. What role does adhesion play in the formation of menisci?

Adhesion is responsible for the curved surface (meniscus) formed by liquids in containers. When adhesive forces between the liquid and container are stronger than cohesive forces within the liquid, a concave meniscus forms (like water in glass). The opposite results in a convex meniscus (like mercury in glass).

20. Can you explain the relationship between cohesion and surface tension?

Cohesion is directly related to surface tension. Stronger cohesive forces between liquid molecules result in higher surface tension. This is why water, with its strong hydrogen bonds, has a higher surface tension than many other liquids.

21. How does the concept of wetting relate to adhesion and cohesion?

Wetting occurs when adhesive forces between a liquid and a solid are stronger than the cohesive forces within the liquid. This causes the liquid to spread out on the solid surface rather than beading up. The degree of wetting depends on the balance between adhesion and cohesion.

22. Why do water droplets form on leaves?

Water droplets form on leaves due to a combination of cohesion and adhesion. Cohesion causes water molecules to stick together, forming droplets, while adhesion allows these droplets to stick to the leaf surface.

23. How does adhesion contribute to capillary action?

Adhesion plays a crucial role in capillary action by causing liquids to climb up narrow spaces against gravity. The liquid molecules adhere to the walls of the capillary tube, pulling the liquid upward.

24. Why does water form a dome-like shape on a penny?

Water forms a dome-like shape on a penny due to cohesion and surface tension. The water molecules are strongly attracted to each other, allowing the water to be held together in a shape that exceeds the penny's edges, despite gravity pulling it down.

25. How does adhesion affect the boiling point of liquids?

Adhesion can affect boiling points indirectly. In a liquid with strong adhesive forces to its container, more energy is required to overcome these forces and form bubbles. This can slightly increase the observed boiling point compared to the same liquid in a container with weaker adhesion.

26. How do adhesion and cohesion contribute to the water cycle?

In the water cycle, cohesion keeps water droplets together in clouds and allows for surface tension in bodies of water. Adhesion helps water stick to soil particles and plant surfaces, aiding in processes like transpiration and soil moisture retention.

27. How does temperature affect cohesive forces in liquids?

As temperature increases, the kinetic energy of molecules increases, weakening cohesive forces between them. This is why surface tension and viscosity generally decrease with increasing temperature in liquids.

28. How do surfactants affect the balance between adhesion and cohesion?

Surfactants lower surface tension by reducing cohesive forces between liquid molecules. They also can increase adhesion between the liquid and other surfaces. This shift in balance allows for better wetting and spreading of the liquid on surfaces.

29. Why does water climb up a paper towel?

Water climbs up a paper towel due to capillary action, which is a result of both adhesion and cohesion. Water adheres to the cellulose fibers in the paper, while cohesion between water molecules pulls more water up behind it.

30. How do adhesive forces contribute to the formation of emulsions?

Adhesive forces are crucial in emulsions. Emulsifiers work by increasing adhesion between two immiscible liquids (like oil and water), allowing tiny droplets of one liquid to remain suspended in the other without separating.

31. What is the difference between specific and non-specific adhesion?

Specific adhesion involves molecular recognition and precise binding between specific molecules, like antibody-antigen interactions. Non-specific adhesion is more general, based on broader physical or chemical properties of the surfaces, like van der Waals forces or hydrogen bonding.

32. How does the concept of work of cohesion relate to surface tension?

The work of cohesion is the energy required to separate molecules of the same substance. It's directly related to surface tension - liquids with higher work of cohesion have stronger cohesive forces and thus higher surface tension.

33. Why do some liquids mix while others don't?

Liquids mix when the adhesive forces between the different molecules are stronger than or comparable to the cohesive forces within each liquid. When cohesive forces dominate, the liquids remain separate, like oil and water.

34. How do adhesion and cohesion affect the formation of soap bubbles?

Soap bubbles form due to a balance of adhesion and cohesion. The soap reduces water's surface tension (cohesion), allowing it to stretch into a thin film. Adhesion between the soap molecules and air on both sides of the film stabilizes the bubble structure.

35. What role do van der Waals forces play in adhesion?

Van der Waals forces are weak intermolecular forces that contribute to adhesion. They are present between all types of molecules and play a significant role in adhesion when stronger forces like hydrogen bonding or ionic interactions are not present.

36. How does the roughness of a surface affect adhesion?

Surface roughness can increase adhesion by providing more contact area for molecular interactions. However, if the roughness is too high, it can reduce contact area and decrease adhesion. The optimal roughness for maximum adhesion depends on the specific materials involved.

37. What is the significance of contact angle in understanding adhesion?

Contact angle is the angle formed where a liquid-vapor interface meets a solid surface. It's a measure of the wettability of a solid by a liquid and indicates the relative strength of adhesive versus cohesive forces. A smaller contact angle indicates stronger adhesion.

38. How do adhesion and cohesion affect the process of painting?

In painting, adhesion allows the paint to stick to the surface being painted. Cohesion within the paint keeps it together as a uniform layer. The balance between these forces affects how well the paint spreads, its thickness, and its durability on the surface.

39. What is the role of adhesion in chromatography?

In chromatography, adhesion between the sample molecules and the stationary phase is crucial. Different components of the sample adhere to the stationary phase with different strengths, causing them to move at different rates and separate from each other.

40. How does the concept of work of adhesion apply to glues and adhesives?

The work of adhesion is a key factor in the effectiveness of glues and adhesives. A good adhesive should have a high work of adhesion with the surfaces it's joining, meaning it requires more energy to separate the adhesive from these surfaces than the surfaces from each other.

41. Why does water form a convex meniscus in a plastic container but a concave one in glass?

This difference is due to the relative strengths of adhesion and cohesion. Water has stronger adhesion to glass than to plastic. In glass, the adhesive forces pull the water up at the edges, forming a concave meniscus. In plastic, the cohesive forces dominate, pulling the surface inward for a convex shape.

42. How do adhesion and cohesion affect the formation of raindrops?

Cohesion causes water molecules in the atmosphere to stick together, forming tiny droplets. As these droplets collide, they coalesce due to surface tension (a result of cohesion). Adhesion to dust particles in the air can provide nucleation sites for droplet formation.

43. What is the relationship between adhesion and friction?

Adhesion contributes to friction between surfaces. When two surfaces are in contact, adhesive forces between their molecules create resistance to sliding motion. This is particularly important in explaining friction at the microscopic level.

44. How does the polarity of molecules affect their adhesive properties?

Polar molecules generally exhibit stronger adhesion to other polar molecules or surfaces due to their ability to form stronger intermolecular forces like hydrogen bonds. Non-polar molecules typically have weaker adhesion, relying mainly on van der Waals forces.

45. What role do adhesion and cohesion play in the function of adhesive tapes?

Adhesive tapes work through a balance of adhesion and cohesion. The adhesive must have strong enough cohesion to maintain its integrity, but also strong adhesion to stick to surfaces. The backing material often has strong cohesion to prevent the tape from breaking apart.

46. How do adhesion and cohesion affect the process of filtration?

In filtration, adhesion between particles and the filter medium helps trap particles larger than the filter pores. Cohesion within the liquid being filtered allows it to pass through the filter as a continuous fluid, while cohesion within larger particles helps keep them intact and trapped.

47. What is the significance of the Young-Dupré equation in understanding adhesion?

The Young-Dupré equation relates the work of adhesion to the surface tensions of the liquid and solid and the contact angle between them. It provides a quantitative way to understand how surface properties affect adhesion, which is crucial in fields like materials science and surface chemistry.

48. How do adhesion and cohesion affect the formation of stalactites and stalagmites?

Adhesion allows water droplets to cling to cave ceilings, while cohesion keeps the droplets together. As the water evaporates, it leaves behind dissolved minerals. Over time, these minerals build up due to both adhesion to the existing formation and cohesion with each other, forming stalactites and stalagmites.

49. What is the role of adhesion in cell biology?

In cell biology, adhesion is crucial for cell-cell and cell-matrix interactions. Cell adhesion molecules on cell surfaces allow cells to stick to each other and to the extracellular matrix, which is essential for tissue formation, wound healing, and many other biological processes.

50. How do adhesion and cohesion affect the properties of polymers?

In polymers, cohesion between polymer chains determines properties like strength and elasticity. Adhesion between the polymer and other materials affects properties like wettability and the ability to form composites. The balance of these forces is crucial in determining the overall behavior of polymer materials.

51. What is the difference between mechanical and chemical adhesion?

Mechanical adhesion occurs when an adhesive hardens within the pores of a surface, creating a physical interlocking. Chemical adhesion involves the formation of chemical bonds (covalent, ionic, or hydrogen bonds) between the adhesive and the surface. Many practical adhesives rely on a combination of both types.

52. How do adhesion and cohesion affect the process of coating surfaces?

In coating processes, adhesion between the coating material and the surface is crucial for durability and effectiveness. Cohesion within the coating material ensures it forms a continuous, uniform layer. The balance between these forces affects properties like thickness, coverage, and resistance to peeling or flaking.

53. What is the role of surfactants in modifying adhesion and cohesion?

Surfactants modify the balance between adhesion and cohesion by reducing surface tension. They can increase wetting and spreading by reducing cohesion within a liquid, and can also modify adhesion between liquids and surfaces. This makes them crucial in processes like cleaning, emulsification, and dispersion.

54. How do temperature changes affect the balance between adhesion and cohesion?

Temperature changes can alter the balance between adhesion and cohesion. Generally, as temperature increases, both adhesive and cohesive forces weaken due to increased molecular motion. However, the rate of change may differ, potentially shifting the balance between these forces and affecting phenomena like wetting and surface tension.

55. What is the significance of adhesion and cohesion in understanding capillary condensation?

Capillary condensation occurs when vapor condenses in small pores at pressures below the saturated vapor pressure of the bulk liquid. This phenomenon depends on both the adhesion between the vapor and pore walls and the cohesion within the condensed liquid. The balance of these forces determines at what pressure condensation occurs in pores of different sizes.

56. How do adhesion and cohesion contribute to the phenomenon of superhydrophobicity?

Superhydrophobicity occurs when a surface is extremely water-repellent. It results from a combination of surface chemistry (low adhesion to water) and surface roughness. The low adhesion causes water to bead up, while the roughness traps air pockets, further reducing contact between water and the surface. Cohesion within the water droplets keeps them as nearly spherical beads on the surface.