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Cohesive and Adhesive Forces

Cohesive force is the force that attracts molecules of the same substance. Adhesive force is the force that binds molecules of different substances together.

We observe various aspects of adhesion and cohesion in our daily lives, including their meaning and examples. These little things keep our lives going on earth, even though, at times, we miss focusing on them. The forces of adhesion and cohesion, despite sounding the same, occur in entirely different ways.  Surface tension describes the relationship between adhesion and cohesion among the physical properties of water. In terms of definitions, adhesion is a property that occurs when two or more molecules are bonded together. Cohesive force, on the other hand, is the force of attraction between molecules.

    Adhesive Forces

    Electrostatic forces exerted by various substances can include adhesion forces. In engineering, adhesive forces refer to the forces attracting unlike substances, such as mechanical forces (sticking together), electrostatic forces (attraction due to opposing charges) and so forth.  When it comes to wetting agents, adhesion causes liquids to cling to surfaces. Force of adhesion refers to the attraction between water molecules and walls of xylem vessels. Many adhesion forces can cause liquids to spread all over the surface. Adhesion resulting from mechanical or electrostatic forces between two different substance classes can cause the liquid to spread.

      Cohesive Forces

      Molecular adhesion, also called cohesive force or cohesive attraction, occurs when molecules are attracted to one another. Cohesive forces relate substances or molecules of similar size and composition. Water is an example of cohesion. When water molecules come together, they form hydrogen bonds to hold them together. Complementary molecules that adhere to each other due to mutual attraction form a cohesive force. Cohesion is responsible for creating surface tension, which ensures a solid-like surface capable of absorbing lightweight or low-density materials. The force of cohesion of water is an excellent example of a cohesive substance. A water molecule is composed of two hydrogens and one oxygen, which is called dihydrogen monoxide (HOH). 

        Difference between Cohesion and Adhesion

        There is no difference between adhesive and cohesive forces. Adhesives are substances that can attach two surfaces or things, such as glue and cement, which can bind certain materials. A sticky bandage describes the bandage. In some cases, adhesive forces relate to the strength of attraction between the adhesive and the substrate. Due to the adhesive force, the adhesive adheres to the substrate. Two or more materials interact with each other to produce this force. Strong and weak bonds are formed in the process.  When hydrogen is shared (hydrogen bonding), there are two possibilities: one is when atoms are shared (covalent bonding) and another when atoms are exchanged (ionic bonding). Contrary to this, cohesive forces are primarily determined by the interactions between molecules within the adhesive or the mechanical adhesion occurring within the adhesive molecules themselves.

          Effects of these Forces

          It is generally believed that cohesive forces and adhesive forces coexist; these forces are found in varying degrees in various activities and processes. In the case of the meniscus, a liquid surface curvature stored in a tube or container, adhesion and cohesion are both responsible.  In physics, adhesion describes the force that holds liquid edges to the container wall. Cohesion is the force of attraction between the water molecules, which causes the liquid surface to curve at its centre. This force also determines the shape of the meniscus. The meniscus will have a convex shape if the cohesion force between liquid molecules is greater than the adhesion force between the liquid and the tube’s inner surface. Mercury, for instance, is enclosed in glass. In the same way, the meniscus will be concave if the adhesion is greater than cohesion –  a glass tube filled with water, for instance. Let us suppose that you spill some water on a surface. If the adhesion equals cohesion, the surface will be horizontal. Water will get absorbed quickly by the surface, and it will also get wet if the adhesive force is strong. Conversely, if the cohesive forces are strong, there will be more attraction between the water molecules than between the surface and the water molecules. This results in less water being absorbed by the surface.

            Conclusion

            A force of attraction is an adhesive or cohesive force. Due to these forces, molecules are attracted or repelled by one another. Molecules are attracted to one another by adhesive forces. An adhesive force is what holds molecules of the same substance together.  Furthermore, adhesive and cohesive forces provide much information about biological processes, such as water transport through xylem tubes.  As a general rule, adhesion and cohesion are the properties of molecules of the same substance sticking together, while adhesion refers to molecules of different substances sticking together.
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