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Ways to Have a Firm Grip on the Subject of Intermolecular Forces

by Nov 3, 2015Chemistry

Intermolecular forces refer to the force of repulsion or attraction which can be found to exist among ions, molecules, atoms and other neighboring particles. Compared with intermolecular forces, which hold together a molecule, these types of forces are weak in nature. For example, covalent bond which is present between molecules of HCL happens to be stronger as compared to the forces which are there among adjoining molecules – which exists whenever the molecules are located close enough to each other. Are you clear on your concepts on Acids and Bases or need to get tips to efficiently solve your paper on Chemical Thermodynamics or on any other topic, professional help can clear all your doubts!

Know what Intermolecular Forces is!

These are actually forces which are present between two individual molecules. This type of force varies from intermolecular force, in which the force happens to be present inside a molecule – such as in the form of covalent or ionic bonds. “Van der Waals forces” is a term that is generally used to describe Intermolecular forces.

When ions or molecules are located very near to each other, intermolecular forces attract them. Intermolecular forces happen to be extremely vital, even though they are comparatively weaker than the forces of attraction present within covalent bonds having energies in 100 – 400 kJ / mol range and oppositely charged ions. In the absence of such kind of force, all types of matter would act like an ideal gas.

Intermolecular forces consist of Coulombic attraction within positive and negative charges. The charges on atoms and ions differ a lot in terms of size, which is also a reason that there is also a marked difference between the strength of intermolecular forces. Materials having strong intermolecular forces usually act as solids at room temperature, while those having extremely weak force between two individual molecules are generally present as gases. Those with moderate amount of intermolecular forces are frequently seen to be present in the form of a liquid at room temperature.

These are forces that molecules apply on one another. These commonly influence the macroscopic properties of the substance in which molecules are only a part. Such kinds of forces can either be repulsive or attractive in type. These molecules are sub-divided, for the purpose of convenience, into two separate groups. These are:

1. Short-range forces –

These come to effect in case the centers of the molecules are isolated from each other by a distance of 3 angstroms or even less.

2. Long-range forces –

These come to effect even when the distance is bigger. Generally, when the molecules fail to chemically interact with one another, there is repulsive type of short-range force. Long-range forces, on the other hand, arise a result of interactions of those electrons which are associated to the molecules and are also known as “exchange forces”. Molecules that chemically interact with one another have attractive exchange forces and are also known as “valence forces”.

How you can have a better grip on intermolecular forces?

1. Be very sure of the concepts! Read up extensive materials from authentic sources to get a comprehensive understanding of the core topics.

2. Be attentive when attending classes. The more you read, the more you can ask your professors and get all your queries cleared. You will be able to soak in the true knowledge of this subject with flair.

3. There is no replacement than taking notes. You must devote time to writing daily by scheduling time for each topic on a daily basis.

4. You must give your best shot to understand the subject giving up the sole inclination to memorize.

5. You must make illustrations, draw charts and graphs with colorful pens to ensure better impression on your brain of this complex subject called intermolecular forces.

Intermolecular Forces: Did you know its history?

Coordinate, ionic and covalent bond arises as a result of forces of attraction which exist between atoms. The Dutch physicist Vander Waal was the first person who in 1873 brought in the existence of forces of attraction between inert gas atoms having completely filled orbitals. This type of force is also there among polar and non-polar molecules. Attractive interactions among various molecules are causes for bringing these molecules close to one another.

“Intermolecular forces” is the name given to attractive interactions among the varied molecules of any substance. In solid matter, these forces have the greatest magnitude. The magnitude lowers when a substance changes to liquid and then gas from a solid state. The liquefaction of gases was demonstrated successfully by Vander Waal depending on the principle of inter molecular forces. These are completely electrostatic forces, which makes them physical in form.

Why are Intermolecular Forces Important?

These forces are especially important in order to let students know about how interaction between molecules occurs. It plays a vital role in deciding properties of varied substances. The energy that is typically needed in order to form the bond is greater than the energy that is needed for breaking apart the molecules.

Types of Intermolecular Forces

Intermolecular forces of attraction are mainly of two types, which differ on degree of strength. We help you to grasp it in a better way!

1. Dipole-dipole Force –

This refers to the force of attraction existing between a dipole present in a specific molecule for the dipole of some other molecule. The strength of this force is based on how strong the dipole is. For instance, there is dipole-dipole force between the molecules of HCL.

2. Ion-dipole Force –

This is the force of attraction between a dipole and an ion – such as an action or an anion. For instance, sodium chloride or NaCl is soluble in water due to the fact that NaCl ions are attracted to dipoles present in a molecule of water.

Induced Intermolecular Forces – These are:

1. Ion induced dipole –

Whenever an ion comes close to a non-polar molecule, the ion is able to affect a dipole in a molecule of non-polar nature. For instance, oxygen is transported by Fe+2 in blood.

2. Dipole induced dipole –

Whenever a dipole comes close to a non-polar molecule, it is able to affect a dipole present in the non-polar molecule. For instance, oxygen is slightly soluble in water.

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