Properties of Liquids Solids Types

1
Properties of LiquidsSolids - Types

• Learning Targets
• Viscosity and surface tension
• Unique properties of water
• Bonding in Solids
• Difference between crystalline solids and
  amorphous solids.

2
Properties of Liquids

• Determined by the nature and strength of
  intermolecular forces of attraction between the
  molecules.
• Two main properties
• Viscosity
• Surface Tension

3
Viscosity

• Friction or resistance to motion existing between
  the molecules of a liquid.
• Stronger force of attraction greater resistance
  to motion. Hence high viscosity.
• Viscosity ?, as Temperature ?.

4
Surface Tension

• The property of the surface molecules in a liquid
  to behave like a thin film or stretched membrane.

5
Surface Tension

• The imbalance of forces on the surface of the
  liquid causes surface tension.
• intermolecular force ? Surface tension ?, so
  surface tension ?, when temperature ?

6
Unusual Properties of Water

• Result from strong hydrogen bonding between polar
  molecules
• High boiling point
• Absorb or release large quantities of heat with
  small changes in temp.
• Density of Ice is less than density of liquid
  water
• Relatively high surface tension
• High heat of vaporization (the amount of heat
  needed to convert liquid to a gas)
• Universal solvent

7
Solids

• Particles in solid states are highly ordered and
  remain in fixed positions.
• Two types of solids
• Crystalline
• Amorphous

8
Crystalline solids

• particles are highly ordered in repeating
  patterns
• Representative or repeating unit is called unit
  cell.
• Break at a specific angle
• Ex snow, sodium chloride, sugar

9
Amorphous solids

• Rigid and appear solid
• Dont have a specific pattern
• Refered to as supercooled liquids
• When heated particles get softer and softer
  before they melt
• Ex glass, rubber, plastics

10
Bonding in Solids

• The physical properties of solids like hardness,
  electrical conductivity, and melting point,
  depend on kind of particles that make up the
  solid and the strength of attractive forces
  between them.
• 4 types
• Metallic solids
• Molecular solids
• Ionic solids
• Covalent network

11
Metallic Solids

• Particles atoms
• Forces metallic bond
• Examples metallic elements

12
Molecular Solids

• Particles atoms or molecules
• Forces hydrogen bonds, dipole-dipole,
  dispersion forces,
• Examples organic compds like CH4, sugar
  (C12H22O11), and some inorganic compds like
  CO2, H2O, SO3

13
Ionic Solids

• Particles cations anions
• Forces electrostatic attractions
• Examples salts of ionic compounds- NaCl, KBr,
  MgSO4

14
Covalent-network solids

• Particles atoms
• Forces covalent bonds
• Examples diamond, graphite, silicon, quartz
  (SiO2)

15
Changes of State

• Also known as phase change
• The conversion of a substance from one physical
  state to another
• Change of state always involves a change in
  energy.

16
Vaporization Condensation

• Vaporization liquid to gas
• Condensation gas to liquid
• Vaporization Vs Evaporation
• The escape of liquid molecules from the surface
  of the liquid.
• Vaporization includes evaporation and boiling.

17
Evaporation

• Rapidly moving molecules on the surface of the
  liquid overcome force of attraction and escape.
• Slower molecules remain in a liquid state, thus
  decreasing average kinetic energy of the liquid
  which is observed by decrease in temp. (known as
  evaporative cooling)
• Evaporation ?, as temperature?.

18
Liquid-Vapor Equilibrium

• Dynamic Equilibrium A state in which two
  opposing processes take place simultaneously.
• The number of molecules entering the gaseous
  state is equal to the number of molecules
  entering the liquid state.

19
Vaporization Condensation

• Boiling Point The temperature at which the vapor
  pressure of a liquid becomes equal to the
  atomospheric pressure.
• Heat of vaporization energy needed to convert a
  certain amount of liquid into gas.
• Condensation is exact opposite of vaporization.

20
Freezing Melting

• Freezing Point The temperature at which solid
  and liquid states of a substance exists together.
• Heat of Fusion The energy needed to convert a
  given amount of a solid into a liquid.
• Freezing is exact opposite of melting. The values
  for the both processes is same with opposite
  signs.
• Freezing (exothermic), ?H is negative
• Melting (endothermic), ?H is positive

21
Sublimation Deposition

• Sublimation solid to gas, the energy change
  associated is called Heat of sublimation.
• Deposition Gas to solid, the energy change is
  Heat of deposition.