Liquids and Solids. Characteristics of Liquids and Solids What properties allow you to classify a...
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Transcript of Liquids and Solids. Characteristics of Liquids and Solids What properties allow you to classify a...
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]