Liquids and Solids

Characteristics of Liquids and Solids

• What properties allow you to classify a substance as a solid, liquid, or gas?

Property Solid Liquid Gas

Volume

Shape

Relative density

Compressibility

Fluid?

Space between particles

Diffusion rate

Motion of particles(amount and type)

Forces between particles?

Surface Tension

• Surface tension is the tendency for liquid surface to contract.

• Depends on IMFs• Compounds that

interfere with the IMFs and reduce surface tension are called surfactants.

Figure 12.18 The molecular basis of surface tension.

hydrogen bondingoccurs in three

dimensions

hydrogen bondingoccurs across the surface

and below the surfacethe net vectorfor attractive

forces is downward

Figure 12.19 Shape of water or mercury meniscus in glass.

adhesive forcesstronger

cohesive forces

H2O

capillarity

Hg

Figure 12.4 Liquid-gas equilibrium.

Figure 12.6

Vapor pressure as a function of temperature and intermolecular forces.

Vapor pressure = the pressure of the vapor resulting from evaporation of a liquid (or solid) above a sample of the liquid (or solid) in a closed container

What factors affect the vaporpressure?

Vapor Pressure

Boiling Point

• Temperature at which the vapor pressure of the liquid = atmospheric pressure

• Normal boiling point vpliquid = 760 mmHg

• condensing point = boiling point

What if…?

• You are camping at a high altitude of 10,000 ft where the atmospheric pressure is 535 mmHg. If you boil an egg for 10 minutes will it be hard-boiled just right, overdone, or runny? Explain your choice.

Subliming Point

• Temperature at which the vapor pressure of the solid equals atmospheric pressure

• Depositing point = subliming point

Iodine subliming

Figure 12.12 Dipole moment and boiling point.

Figure 12.13 Hydrogen bonding and boiling point.

Figure 12.16 Molecular shape and boiling point.

more points for dispersion

forces to act

fewer points for dispersion

forces to act

Freezing Point

• Temperature at which liquid and solid are in equilibrium

• Not affected by pressure but does depend on IMFs and molar mass

• Melting point = freezing point

Figure 12.21 The hexagonal structure of ice.

Figure 12.22 The striking beauty of crystalline solids.

portion of a 3-D lattice

Figure 12.23 The crystal lattice and the unit cell.

lattice point

unit cell

portion of a 2-D lattice

unit cell

Figure 12.27

Diffraction of x-rays by crystal planes.

Table 12.5 Characteristics of the Major Types of Crystalline Solids

ParticlesInterparticle Forces

Physical Behavior Examples (mp,0C)

Atomic

Molecular

Ionic

Metallic

Network

Group 8A(18)[Ne-249 to Rn-71]

Molecules

Positive & negative ions

Atoms

Atoms

Soft, very low mp, poor thermal & electrical conductors

DispersionAtoms

Dispersion, dipole-dipole, H bonds

Fairly soft, low to moderate mp, poor thermal & electrical conductors

Nonpolar - O2[-219], C4H10[-138], Cl2

[-101], C6H14[-95]

Polar - SO2[-73], CHCl3[-64], HNO3[-42], H2O[0.0]

Covalent bond

Metallic bond

Ion-ion attraction

Very hard, very high mp, usually poor thermal and electrical conductors

Soft to hard, low to very high mp, excellent thermal and electrical conductors, malleable and ductile

Hard & brittle, high mp, good thermal & electrical conductors when molten

NaCl [801]CaF2 [1423]

MgO [2852]

Na [97.8]Zn [420]Fe [1535]