Adhesive force is the force of attraction that exists between the molecules of two different substances. This force is accountable to bind the two objects together. Mostly, adhesion exists between a solid and a liquid substance. It comes under the intramolecular interactions. Adhesion includes electrostatic attraction. It is the natural glue that helps the molecules of two different objects to stick to each other. Adhesive force may be wanted or unwanted in nature. For example, wetting of surface, painting, storing liquids, etc. all are possible only due to the existence of adhesive force between the molecules of the substances involved.
Examples of Adhesive Force
Applying a coat of paint on the walls is one of the perfect examples of adhesive force in action. The process involves depositing a polymer layer on the surface of the wall. The force of attraction acting between the molecules of paint and the wall help the coating of paint to be deposited over the wall and is called the adhesive force. The stronger be this force of attraction, the longer will be the life of paint coating on the wall. It can be improved by improving the substrate.
2. Wet Surface
When water falls on any surface, it spreads out thoroughly. This spreading of water causes an intramolecular interaction to get developed between the water molecules and the surface molecules. The force of attraction between the molecules of two different substances is called the adhesive force. Hence, adhesive force is responsible for the floor to get wet when a liquid is poured onto it.
The curvature formed by the liquids when poured into a container is known as the meniscus. The meniscus can be either concave or convex. When the cohesive force between the molecules of the liquid and the molecules of the container wall is stronger than the adhesive force between the molecules of the liquid and the wall, a convex meniscus can be seen. This convex meniscus gets developed in order to reduce contact with the surface of the wall. For example, mercury. When the adhesive force is stronger than the cohesive force present, the liquid gets attracted more towards the wall than the neighboring molecules. Hence, a concave meniscus is observed. For example, water.
When a liquid substance with high viscosity is poured and stored in a jar, it often sticks to the container walls. This is due to the adhesive force existing between the container molecules and the molecules of the liquid. Whereas, the cohesive force is responsible to bind the molecules of the same substance together. If cohesive force is sufficiently more than the adhesive force, the molecules get closely attracted to each other, and the substance is said to possess a non-stick nature.
5. Butter on Bread
When the butter is melted, it gets converted to liquid form. After melting it becomes easier to apply this liquid form of butter on the solid bread. A force exists between a liquid and a solid substance that helps to hold them together. This force is known as the adhesive force and allows the butter to spread evenly on the surface of the bread.
6. Icing on Cake
The frosting and cream applied on the surface of properly baked cake make use of adhesive force. The icing on the cake serves to decorate and add taste to it. The interaction between the molecules of icing and the molecules of the cake base is thoroughly intramolecular. Hence, a considerable amount of adhesion is said to be existing.
Putting on makeup is one of the most common daily life activities that involve the concept of adhesion. The cosmetic products do not get off the skin easily. It requires an external force to remove makeup from the face. The force that helps the products to stay in contact with the skin is known as the adhesive force. It helps the makeup molecules to stick to the skin molecules unless acted upon by an external force in order to remove it.