Short Answer

Nonpolar molecules dissolve in nonpolar solvents because both have similar types of weak intermolecular forces. Since neither has positive or negative charges, they interact through London dispersion forces. These forces allow the solvent to surround the solute and mix it evenly.

This follows the principle “like dissolves like.” Nonpolar solvents can separate and spread nonpolar solute molecules because the energy needed to break the solute–solute forces is balanced by the energy released when solute–solvent interactions form.

Detailed Explanation :

Nonpolar Molecules Dissolve in Nonpolar Solvents

Nonpolar molecules do not have charge separation. Their electrons are evenly shared, so they do not have partial positive or partial negative ends. Because of this, the only forces acting between nonpolar molecules are London dispersion forces, which are very weak. A nonpolar solvent also has the same type of weak forces. When a nonpolar solute is placed in a nonpolar solvent, the weak forces between solute molecules can be replaced by similar forces between solute and solvent molecules.

This makes dissolution possible because the solvent can separate the solute particles and distribute them throughout the solution. Since the forces involved are similar in nature and strength, the process is energetically favorable. Examples include oil dissolving in gasoline and iodine dissolving in carbon tetrachloride.

Thus, the rule “like dissolves like” explains why nonpolar substances dissolve in nonpolar solvents.

1. Nature of Nonpolar Molecules

Nonpolar molecules have:

• No charge separation
• Uniform electron distribution
• No permanent dipole moment

Examples of nonpolar molecules include methane (CH₄), oxygen (O₂), nitrogen (N₂), benzene (C₆H₆), and carbon tetrachloride (CCl₄). These molecules interact weakly with one another. Because they lack polarity, they do not dissolve in polar solvents like water.

2. Nature of Nonpolar Solvents

Nonpolar solvents such as hexane, benzene, and toluene also do not have dipoles. The only attractive force present in them is the London dispersion force. These solvents are ideal for dissolving nonpolar substances because they create an environment where the solute can interact with the solvent on equal terms.

Nonpolar solvents are widely used to dissolve oils, fats, waxes, and hydrocarbons.

3. Role of London Dispersion Forces

London dispersion forces arise due to temporary shifts in electron distribution, creating momentary dipoles. These forces are:

• Weak
• Temporary
• Present in all molecules, but dominant in nonpolar ones

When a nonpolar solute is placed in a nonpolar solvent:

• Temporary dipoles in the solvent induce temporary dipoles in the solute.
• Weak attractions form between solute and solvent molecules.
• These interactions help separate and spread solute molecules throughout the solvent.

Although weak, these forces are sufficient because both solute and solvent rely on the same type of attraction.

4. Energetic Favorability of Dissolution

A solute dissolves when:

• The solute–solute forces can be broken
• The solvent–solvent forces can be adjusted
• New solute–solvent interactions release enough energy to balance or exceed the energy needed

In nonpolar systems:

• Breaking solute–solute interactions requires very little energy.
• Forming solute–solvent interactions also releases a small but matching amount of energy.

Since the forces are similar, the dissolution process becomes energetically neutral or favorable.

5. Principle of “Like Dissolves Like”

This principle states that substances with similar intermolecular forces dissolve in one another. For nonpolar systems:

Nonpolar solute + Nonpolar solvent → Stable solution

Oil dissolves in kerosene, butter dissolves in benzene, and wax dissolves in nonpolar organic solvents. However, these same substances do not dissolve in water because polar solvents cannot interact strongly enough with nonpolar molecules.

6. Solvation Process in Nonpolar Media

When dissolution occurs:

1. Solvent molecules move between solute molecules.
2. Solvent pushes solute molecules apart.
3. Solute becomes surrounded by solvent molecules.

This process is called solvation. In nonpolar dissolution, solvation is driven entirely by dispersion forces.

Because these forces are similar among all molecules in the mixture, the solute remains evenly spread without separating or settling.

7. Why Polar Solvents Cannot Dissolve Nonpolar Solutes

Water and other polar solvents cannot dissolve nonpolar molecules because:

• Polar solvents have strong dipole–dipole or hydrogen bonding forces.
• Nonpolar molecules cannot form strong interactions with them.
• The energy cost of breaking solvent–solvent forces is too high.

Therefore, nonpolar molecules separate rather than dissolve.

Conclusion

Nonpolar molecules dissolve in nonpolar solvents because both contain weak London dispersion forces. These similar forces allow the solvent to separate and surround solute molecules easily. The energy changes during dissolution are balanced, making the process stable and favorable. This behavior follows the principle “like dissolves like,” which explains why nonpolar substances dissolve only in nonpolar solvents.