Liquids, Solids, and Intermolecular Forces Notes (CHAPTER 12)

Properties of States of Matter

• Gas: Low density, indefinite shape and volume, weak intermolecular forces (e.g., $CO_2$).
• Liquid: High density, indefinite shape, definite volume, moderate intermolecular forces (e.g., $H_2O$).
• Solid: High density, definite shape and volume, strong intermolecular forces (e.g., $C<em>{12}H</em>{22}O_{11}$).

Physical Properties of Liquids

• Surface tension: Resistance to increase surface area.
• Viscosity: Resistance to flow.
• Vapor pressure: Pressure exerted by gas molecules above a liquid when evaporation and condensation rates are equal.
• Boiling point

Surface Tension

• Resistance of a liquid to increase its surface area.
• Water drops are spherical due to surface tension from attractive forces between water molecules.

Viscosity

• A liquid's resistance to flow.
• Greater attraction between molecules results in higher viscosity.

Water

• Freezes at $0°C$.
• Boils at $100°C$ at 1 atm.
• Density of liquid water is $1.00 g/mL$, and ice is $0.917 g/mL$.
• Specific Heat Capacity = $4.18 J g^{-1}°C^{-1}$.

Heating Curve

• Heat added to a solid increases its temperature to the melting point (Heat of Fusion).
• Further heat raises the liquid's temperature to the boiling point (Heat of Vaporization).

Vapor Pressure

• Vaporization: Liquid molecules escape into the vapor state.
• Condensation: Vapor molecules return to the liquid state.
• Vapor pressure is the pressure exerted by gas above liquid when evaporation and condensation rates are equal.

Intermolecular Attractions

• Much weaker than ionic or covalent bonds.
• Dispersion Forces: Attractions between non-polar molecules (temporary dipoles).
• Dipole-to-Dipole: Attraction due to molecular polarity.
• Hydrogen Bond: Strong dipole-dipole attraction (e.g., in water).
• Ion-Dipole: Between ionic and polar compounds.

London Dispersion Forces

• Temporary, present in all molecules.
• Size depends on number of electrons and molecular shape.
• Larger molar mass = Larger induced dipole.

Dipole-to-Dipole Attractions

• Strength depends on bonded atoms and molecular shapes.
• Stronger than induced dipole attractions individually.

Hydrogen Bonding

• Occurs in molecules with O–H, F–H, or N–H groups.
• Results in high melting/boiling points and water solubility.

Attractive Forces and Properties

• Larger attractive forces mean higher boiling and melting points.
• "Like dissolves Like": Polar in polar (water, alcohol), non-polar in non-polar (oils, gasoline).
• Molecules with O or N have higher water solubility due to H-bonding.