Cohesion is a fundamental part of the physics of many materials, both soft and hard. The basic idea is that certain molecules, or atoms, stick or bind together to form larger structures with different properties. For instance, the hydrogen bond forms between two hydrogen atoms and other molecules, such as oxygen, to create the basis of the water molecule. Cohesion also plays an important role in the study of solids, liquid, and gas states of matter.
In an applied context, the concept of cohesion is also used in designing and creating materials for various applications. For example, in designing materials for automotive, aerospace, chemical and other industries, cohesion is an important factor in determining the performance of the material. Moreover, understanding the relationship between the cohesive forces and the properties of a material helps scientists and engineers develop composite materials with unique properties. For instance, coating materials with a layer of polymer or other materials can create stronger cohesive forces to increase the mechanical strength of the material.
The magnitude and direction of a cohesive force are determined by several factors, such as the chemical bond between molecules and their size, shape, and dipole moment. The molecular dipole moments will cause oppositely charged molecules to attract, while those with the same polarity will generally repel each other. Hence, the magnitude and direction of a molecule’s dipole moment will determine the kind of cohesive force it experiences and its effect on the overall cohesive force.
Generally, the strongest cohesion is observed in covalent bonds, which is the result of shared electrons. In this case, two atoms share electrons, forming a covalent bond, and the energy derived from such sharing of electrons results in a cohesive force between the two atoms. Alternatively, metallic bonding takes place when different metals are present, resulting from the transfer of electrons in the intermetalic bonding space. The metallic bonding will result in a cohesive force that is greater than that of other physical bonds. The hydrogen bond is also a form of cohesion, which results in water molecules being attracted to each other.
Apart from material science, cohesive forces are also important in any environment where liquids and solids are present. In liquid-solid materials, molecules may be clustered around a solid surface, resulting in an increase of cohesion. Such an effect is known as surface tension, and is a result of the attractive cohesive forces between molecules of different substances. Cohesion can also explain the levitating force of water in air, which is called the water adhesion force.
In conclusion, cohesive forces form the basis of many physical properties of materials. The magnitude and direction of a cohesive force are determined by several factors, such as the type of the chemical bond, the size, shape and dipole moment of the atoms involved. Such forces are ubiquitous across a range of applications, from material engineering and design to environmental sciences. Their importance is undeniable, and understanding how these forces work is crucial for continued advancements in technological and scientific pursuits.
