1️⃣ Polarity Affects Intermolecular Forces (IMFs)

✅ Intermolecular Forces

These are forces between molecules (not within the bond).
They control how molecules attract each other.

The three major IMFs are:

A. Hydrogen Bonding (Strongest)

Happens when a molecule has:
✅ H bonded to F, O, or N

Examples: H₂O, NH₃, HF

Effect: very strong attraction → higher boiling point, high surface tension.

B. Dipole–Dipole Forces (Medium)

Happens between polar molecules because δ⁺ and δ⁻ attract each other.

Examples: HCl, SO₂

Effect: stronger than dispersion → higher melting/boiling point than nonpolar.

C. Dispersion Forces (Weakest)

Happens in all molecules, but only IMF for nonpolar ones.

Examples: CH₄, CO₂, O₂

Effect: weaker attraction → lower boiling/melting point.

📌 Key Rule:
More polarity = stronger IMF = more “stickiness” between molecules.

2️⃣ Polarity and Solubility

✅ “Like dissolves like”

A substance dissolves in another if they have similar polarity.

• Polar dissolves polar
  
  

• Nonpolar dissolves nonpolar
  
  

Examples

✅ Salt dissolves in water (polar–polar)
✅ Sugar dissolves in water (polar–polar)
❌ Oil does not dissolve in water (nonpolar vs polar)
✅ Oil mixes with gasoline (nonpolar–nonpolar)

Why?

Polar molecules attract polar molecules.
Nonpolar molecules attract nonpolar molecules.
Different polarity = weak attraction = no mixing.

3️⃣ Polarity and Boiling / Melting Points

✅ Polarity increases boiling & melting points

Because stronger attractions need more energy to break.

General pattern:

• Hydrogen bonding → highest BP/MP

• Dipole–dipole → moderate BP/MP

• Dispersion only → lowest BP/MP

4️⃣ Polarity and Surface Tension / Viscosity

✅ Surface Tension

Polarity strengthens molecule attraction at the surface.

Example:
Water has high surface tension because of hydrogen bonding, so droplets form and insects can walk on it.

✅ Viscosity

Polarity makes molecules “stick” more → flow becomes slower.

Example:
Honey and syrup are more viscous than alcohol because their molecules attract strongly.

5️⃣ Real-Life Applications of Polarity

🧼 A. Soap and Cleaning

Soap molecules have two ends:

• Polar head (water-loving)

• Nonpolar tail (oil-loving)
  
  

So soap can connect water + oil, letting dirt wash away.

🛢️ B. Oil + Water

Oil is nonpolar, water is polar → they separate.
This is why fats float in soups or on rivers after spills.

🍶 C. Alcohol + Water

Alcohol is partly polar → mixes with water easily.
This is why hand sanitizer blends alcohol and water.

🧪 D. Solvents

• Water = polar solvent

• Gasoline / hexane = nonpolar solvent
  
  

Used depending on what needs to dissolve.

7️⃣ Quick Comparison Table (Polar vs Nonpolar Properties)