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Affect of Intermolecular Forces | ChemTalk .

Core Ideas

On this article, you’ll study concerning the results of intermolecular forces (IMFs). You’ll perceive how intermolecular forces affect the bodily properties of matter, equivalent to melting level, viscosity, and floor stress.

Subjects Coated in Different Articles

What are Intermolecular Forces?

Intermolecular forces (IMFs), as its identify would recommend, are forces between molecules. They’re electrostatic interactions between charged molecules. Although IMFs embody each engaging and repulsive interactions, the time period is normally solely used for engaging interactions between molecules (having sturdy IMFs between two molecules means the pressure of attraction between the 2 is powerful).

There are various kinds of intermolecular forces: London dispersion forces, dipole-dipole forces, ion-dipole forces, and hydrogen bonding. Intermolecular forces have various strengths, and the energy of the intermolecular forces inside a substance influences the substance’s bodily properties, together with boiling/melting factors, viscosity, floor stress, vapor stress, and so on.

How Intermolecular Forces Affect Bodily Properties

Boiling/Melting factors

The boiling level is the temperature at which a liquid can flip right into a gasoline, and the melting level is the temperature at which a stable can flip right into a liquid.

Having sturdy intermolecular forces signifies that the attraction between the molecules is powerful. Due to this fact, if a substance has stronger IMFs, it’s more durable to tug its molecules away from one another, ensuing within the substance having a better boiling level and melting level.

For instance, propane (C3H8), has a boiling level of -42°C whereas methane (CH4), has a boiling level of -161.6°C. Propane has such a better boiling level than methane as a result of it has stronger London dispersion forces (bigger molecule) and stronger IMFs total than methane.


One other impact of intermolecular forces is viscosity. Viscosity is the measure of a fluid’s resistance to circulate. A excessive viscosity leads to a thicker and stickier fluid. Viscosity is a results of intermolecular forces. Stronger intermolecular forces trigger a fluid to have a stronger attraction to itself, giving it a excessive viscosity.

Glycerol, for instance, has a lot stronger intermolecular forces than water as a result of it accommodates 3 -OH hydroxyl teams able to hydrogen bonding, whereas water solely has one. Because of this water flows very effectively whereas glycerol doesn’t.

example of intermolecular forces and viscosity
Honey is sticky and flows slowly on account of its sturdy intermolecular forces. Supply.

Vapor Stress and Volatility

The energy of the intermolecular forces of a liquid impacts the liquid’s vapor stress. Vapor stress is the stress exerted by vapor on the floor of a liquid. A rise in volatility, which is the tendency of a substance to evaporate, leads to a rise in vapor stress. Stronger intermolecular forces give a liquid a stronger attraction to itself. This makes it more durable for the liquid to evaporate, leading to decrease volatility and decrease vapor stress.

Floor Pressure

One of many results of intermolecular forces is floor stress. Floor stress is the elastic property of the floor of a liquid, equivalent to how water drops kind a spherical form. This property is brought on by intermolecular forces, which maintain the molecules collectively and trigger the floor of the liquid to withstand exterior forces. The stronger the intermolecular forces, the larger the floor stress.

example of water surface tension and imfs
A water droplet maintains its “bubble” form due to floor stress. Supply.


One other one of many results of intermolecular forces is solubility. The stronger the intermolecular forces between the solute and solvent, the larger the solubility. The phrase “like dissolves like” helps predict the solubility of a solute in a solvent. Polar molecules dissolve polar molecules by means of dipole-dipole forces, and nonpolar molecules dissolve nonpolar molecules by means of London dispersion forces. Polar molecules and nonpolar molecules don’t dissolve effectively with one another.

Affect of Intermolecular Forces Apply Issues

Order the next compounds from lowest boiling level to highest:

  • Helium gasoline He
  • Isobutyl alcohol C4H10O
  • Acetone (CH3)2CO
  • Water H2O

Affect of Intermolecular Forces Options

Answer: Helium gasoline, Acetone, Water, Isobutyl alcohol

Clarification: Since having stronger intermolecular forces will increase boiling level, this downside is to rank the compounds from weakest to strongest intermolecular forces. Helium Fuel is the smallest molecule right here and is simply able to London dispersion forces, so it has the bottom boiling level. Acetone is able to dipole-dipole forces however not hydrogen bonding, which water and Isobutyl alcohol are able to, so acetone has the second lowest boiling level. Water and Isobutyl alcohol each have one -OH hydroxyl group, however Isobutyl alcohol is bigger and has stronger London dispersion forces, so Isobutyl alcohol has the best boiling level.



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