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Usually, adhesion is when two or more molecules, mostly different in nature, tend to bond with one another. While, the intermolecular force of attraction typically between two molecules that are similar in nature is cohesion. These are essentially part of our lives, but we usually overlook most of these.
Check More: Viscosity
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Key Takeaways: Adhesion and Cohesion Difference, Adhesion, Cohesion, Electrostatic force, Van der waals force,
Cohesion Definition
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Cohesion, as is also mentioned prior, is a property of molecules, typically similar in nature, to bond with one another. Cohesive forces correspond to Van Der Waals forces and hydrogen bonding that often cause liquid substances, much like water, to hold out against separation. For instance, when a glass is poured with a liquid substance, adhesive and cohesive forces together make an impact to withstand any force of separation. strong cohesive forces help create droplets of water on the surface.
Adhesion Definition
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Adhesion, on the opposite side, is the property of molecules, mainly different in nature, to bond with one another. For instance, solid substances usually have a high cohesive tendency which is why they try sticking to surfaces they connect to. Adhesive forces mainly result due to electrostatic forces, especially exerted on different substances which have contrasting properties. Strong adhesive forces cause liquid substances, like water, to outspread over the given surface. However, in most cases, both phenomena vary in strength, especially based on the nature of the surroundings.
Adhesion and Cohesion
Difference Between Adhesion and Cohesion
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Adhesion and cohesion vary in nature, but still co-exist with one another. Here are differences between the both of them.
| Adhesion | Cohesion |
|---|---|
| Forces of Adhesion occur between two distinct molecules, different in nature. | Forces of cohesion occur between molecules similar in nature. |
| It is an attraction held between water molecules and the container or tube wall. | It is usually the attraction between similar molecules, like water. |
| The effect of meniscus and capillary action are mainly impacted due to adhesion. | Cohesion is the effect made by meniscus, surface tension, and capillary action. |
| It causes liquid surfaces to outspread over the surface it is contained. | It results in the formation of water droplets on the container. |
| It is caused due to electrostatic or mechanical forces that often reside amongst two or more dissimilar substances. | Cohesion is often caused either by Van Der Waals forces or hydrogen bonding. |
Also Check: Surface Tension of Water By Capillary Rise Method
Relationship Between Adhesion and Cohesion
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The relationship between cohesion and adhesion remains constant since they exist together. For instance, meniscus – a curve upon the surface of a substance, especially water, when poured in a tube – usually occurs due to the existence of both adhesion and cohesion together.
In simple words, the force of attraction between liquid edges and the wall of the tube or container is mainly due to adhesion. While, the force of attraction between the water molecules itself, which is responsible for causing the liquid surface to take the shape of a curve midway, is an outcome of cohesion.
The shape of the meniscus is often due to these forces acting together to put an impact. Simply, when the cohesive forces between water molecules are relatively less, as opposed to the adhesive forces between the water molecules and the tube, the surface tends to curve upwards. One of the biggest instances of the event is when water is poured in a glass canister.
Also Read: Characteristics of particles of matter
Things to Remember
- Adhesion and cohesion naturally co-exist with one another, and often impact together.
- Cohesion is a property of molecules, typically similar in nature, to bond with one another.
- Adhesion is the property of molecules, mainly different in nature, to bond with one another.
- Meniscus of a liquid, especially water, is its movement either upward or downward that causes the formation of a curve seen at the very edge of the liquid in a tube.
- One of the major differences between adhesion and cohesion is that adhesion is the force of attraction between liquid edges and the tube wall, while the attraction force between the water molecules itself causing the curve midway is an outcome of cohesion.
Also Read: Variation in Volume with Pressure for Sample of Air at Constant Temperature
Sample Questions
Ques. What is Cohesion? Mention one major example. (3 marks)
Ques. Define the meaning of Adhesion. Give an instance of the same. (2 marks)
Ans: Adhesion is the property of heterogeneous molecules, which are different in nature, to bond with one another. Adhesive forces are caused by electrostatic forces, mainly exerted on different substances which have dissimilar properties. In simple words, it comprises mechanical forces (that help molecules stick together), and electrostatic forces (opposing charge attraction) together that give rise to adhesive properties. One major instance of adhesion is capillary action where water molecules strongly become attracted towards molecules dissimilar from it.
Ques. What makes the process of cohesion important? (2 marks)
Ans: Cohesion is especially important from the transportation of water to all parts of a tree or a plant. In simple terms, it permits the formation of surface tension that helps a liquid surface to contract as much as possible. Moreover, this is a known phenomenon that causes liquid surfaces, especially water, to withstand rupture when placed under any sort of tension. Besides, cohesion has been widely known to navigate water’s boiling point, especially helping animals regulate the temperature of their bodies.
Ques. List the relationship between adhesion and cohesion. (2 marks)
Ans: Adhesion and cohesion mainly co-exists in nature, while still being slightly different.
- The force of attraction between liquid edges and container wall is mainly due to adhesion. While, the force of attraction between the water molecules itself, that causes liquid surfaces to take the shape of a curve midway, is a result of cohesion.
- The shape of the meniscus is often due to these forces acting together to put an impact. Quite so, when the cohesive forces between water molecules are relatively less, as opposed to the adhesive forces between the water molecules and the tube, the surface tends to curve upwards.
Also Read: Electrolytic Cells and Electrolysis
Ques. What is a meniscus? (3 marks)
Ans: The Meniscus of a liquid surface is its movement followed either upward or downward that causes the formation of a curve seen at the very edge of the liquid in a tube or container. The visible nature of the curve, either upward or downward, is usually determined by the surface tension upon the liquid, alongside the adhesion capacity it has against the container or tube wall. Mainly, a convex or upward meniscus seems to occur when liquid molecules tend to be strongly attracted to one another, rather than the container wall – while considering the contrary for a downward curve.
Ques. List the differences between Adhesion and Cohesion. (5 marks)
Ans: The differences are:
| Adhesion | Cohesion |
|---|---|
| Forces of Adhesion occur between two dissimilar molecules. | Forces of cohesion occur between molecules similar in nature, like liquid molecules themselves. |
| Adhesion is an attraction between water molecules and the container or tube wall. | Cohesion usually is the attraction between similar molecules. |
| Capillary action, alongside meniscus are largely impacted due to adhesion. | Cohesion is the effect made by meniscus, surface tension, and capillary action. |
| It causes liquid surfaces to outspread over the surface it is contained. | It results in the formation of water droplets on the container. |
| It is caused due to electrostatic or mechanical forces that often reside amongst two or more dissimilar substances. | Cohesion is often caused either by Van Der Waals forces or hydrogen bonding. |
Ques. What are some integral benefits of adhesion and cohesion? (2 marks)
Ans: Capillary action, in chemistry, has impacted human health positively since it involves action of cohesion and adhesion. In a nutshell, adhesion and cohesion are one of the most significant water properties that impacts the way liquid surfaces, like water, works – from our body to trees. Cell adhesion, a larger part of cellular biology, helps the formation of multicellular organisms. Adhesion also simultaneously helps blood freely move through animal bodies.
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