Question

Define the following terms, and describe how each depends on the strength of the intermolecular forces.

a. surface tension d. boiling point

b. viscosity e. vapor pressure

c. melting point

Short answer

a.Surface tension:

Surface tension is known as the tendency of any liquid surface at rest to shrink into the minimum surface area possible. Surface tension is a unique property of liquids that depends on the nature of intermolecular interactions between the molecules of liquids. An increase in the intermolecular interactions between the molecules causes the surface tension to increase.

b.Viscosity:

The viscosity of a fluid is used to measure the resistance to deformation of fluid at a given rate.

Intermolecular forces are essential in defining viscosity because molecules have strong attractions between them. It causes them to resist flow more strongly.

c.Melting point

The melting point of a substance is the temperature at which substances change state from solid to liquid. When a strong intermolecular force acts between the molecules of substances, more energy is needed to melt the molecules. So the melting point is higher.

d.Boiling point

The boiling point of a substance is the temperature at which the vapor pressure is equal to the standard sea-level atmospheric pressure. Compounds with strong intermolecular forces between their molecules will have higher boiling points.

e. Vapor pressure

Vapor pressure is used to measure the tendency of a material to change into the gaseous or vapor state, increasing with temperature. A liquid's vapor pressure is directly related to the intermolecular forces present between its molecules. The stronger these forces, the lower the rate of evaporation and the lower the vapor pressure.

Step-by-step solution

Intermolecular force

Intramolecular forces are well-known forces that work between the molecules as they hold atoms of the molecule together within a molecule.Intermolecular forces exist between molecules of any compound, such as water molecules.

Types of intermolecular forces

There are mainly four types of intermolecular forces present.

1. London dispersion forces

2. Dipole-Dipole interactions

3. Hydrogen bonding

4. Ion-Dipole force

Explanation

a.Surface tension-

Surface tension is known as the tendency of any liquid surface at rest to shrink into the minimum surface area possible. Surface tension is a unique property of liquids that depends on the nature of intermolecular interactions between the molecules of liquids. An increase in the intermolecular interactions between the molecules will also increase the surface tension.

b.Viscosity

The viscosity of a fluid is used to measure the resistance to deformation of fluid at a given rate.

Intermolecular forces play an important role in defining viscosity because molecules have strong attractions between them. It causes them to resist flow more strongly.

c.Melting point

The melting point of a substance is the temperature at which substances change state from solid to liquid. When a strong intermolecular force acts between the molecules of substances, the more energy is needed to melt the molecules, the higher the melting point.

d.Boiling point

The boiling point is the temperature at which the vapor pressure is equal to the standard sea-level atmospheric pressure. Compounds with strong intermolecular forces between their molecules will have higher boiling points.

e. Vapor pressure

Vapor pressure is used to measure the tendency of a material to change into the gaseous or vapor state, increasing with temperature. A liquid's vapor pressure is directly related to the intermolecular forces present between its molecules. The stronger these forces, the lower the rate of evaporation and the lower the vapor pressure.