Ch.1 Intermolecular forces

• Polar Covalent Forces:

  • Hydrogen bonds
  • Dipole-dipole forces
  • Ion-dipole forces
• Nonpolar Covalent Forces:

  • Dispersion Forces
  • Van der Waals Force
• Solids:

  • IMF between neighboring particles are strong enough to keep them locked in position
  • Not very compressible like liquids due to lack of space between particles
  • If particles are in highly ordered packing arrangement, the structures are crystalline
• Liquids:

  • IMF are strong enough to hold particles together, but not strong enough to prevent molecules from moving or sliding over one another
  • Can flow, be poured, and assume the shape of their containers
  • More dense and less compressible than gases
  • Has definite volume, independent of size and shape of their container
• Water:

  • Covalently bonded with tetrahedral geometry and 104.5 degrees bond angle
  • No net electric charge, but has polarity
• Solids:

  • Have definite volume and shape
  • Rigid and cannot be compressed easily
  • Do not diffuse into another solid easily
  • Do not flow and can be stored in a container
  • Usually change into their liquid state when heated
• Phase Diagram of Water:

  • Summarizes the effect of pressure and temperature on water in a closed container
  • Shows the different phases of water under varying conditions
• Solid

  • Has strong IMF and orderly arranged molecules
  • Rigid and cannot be compressed easily
  • Does not diffuse into another solid easily
  • Does not flow and can be stored in a container
  • Usually changes into its liquid state when heated
• Liquid

  • IMF are strong enough to hold particles together, but not strong enough to prevent molecules from moving or sliding over one another
  • Can flow, be poured, and assume the shape of their containers
  • More dense and less compressible than gases
  • Has definite volume, independent of size and shape of their container
• Gas

  • IMF are not strong enough to hold particles together, allowing them to move freely
  • Can expand to fill any container
  • Less dense and highly compressible compared to liquids and solids
• Matter is made of particles that are constantly in motion (kinetic energy)

  • The amount of kinetic energy in a substance is directly proportional to its temperature
  • The amount of space in between particles is related to the substance's state of matter
  • Phase changes happen when the temperature of the substance changes sufficiently
  • As the strength of the intermolecular forces increases, the particles get closer together
• Intermolecular forces try to draw the particles together

  • Factors affecting the state of a substance include temperature and pressure
  • Heating and cooling changes the kinetic energy of the particles, thus affecting the physical state
  • Increasing pressure increases the strength of IMF
• Surface Tension:

  • Cohesive forces between liquid molecules
  • Allows small objects to "float" on the surface of the fluid
  • Examples include walking on water and clinical tests for jaundice
• Viscosity:

  • Resistance to flow of a fluid
  • Can be measured using dynamic/absolute/simple viscosity or kinematic viscosity
  • Capillary viscometer measures the rise or depression of a liquid in a small passage
• Vapor Pressure and Boiling Point:

  • Tendency of particles to escape from the liquid at a given temperature
  • Volatile substances have high vapor pressure at normal temperature
  • Boiling point is the temperature at which vapor pressure equals atmospheric pressure
• Molar Heat of Vaporization:

  • Energy required to transform a given quantity of a substance from liquid to gas at a given pressure
• Electricity:

  • Flow of electrons from one place to another
  • Electrical insulators do not conduct electricity
• Thermal Conductivity:

  • Heat insulators have low heat conductivity
• Malleability:

  • Ability to hammer a solid into a sheet without breaking it
• Ductility:

  • Ability to stretch a solid to form a wire
• Melting Point:

  • Depends on the strength of the IMF
  • Different substances have different melting points based on their bonding
• Solubility:

  • Extent to which a solid dissolves in a particular solvent
  • Dissolving a molecular solid requires breaking only weak IMFs
• Density:

  • Amount of mass per unit volume
  • Solids have a definite volume and shape, are rigid, and cannot be compressed easily
• Crystalline and Amorphous Solids:

  • Crystalline solids have an orderly internal structure, while amorphous solids do not
• Polar Covalent Forces:

  • Hydrogen bonds occur between polar molecules with highly electronegative atoms
  • Dipole-dipole forces occur between oppositely charged poles of polar molecules
  • Ion-dipole forces occur between an ion and a polar molecule
• Nonpolar Covalent Forces:

  • Dispersion Forces are weak IMFs that arise from interactive forces between instantaneous/induced dipoles
  • Van der Waals Force allows molecules to attract each other at moderate distances and repel at close range
• Summarizes the effect of pressure and temperature on a substance in a closed container

  • Shows the different phases of a substance under varying conditions
• If a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change to reestablish an equilibrium
• Covalent bonds determine:

  • Molecular shape
  • Bond energies
  • Chemical properties
• Intermolecular forces (non-covalent bonds) influence:

  • Physical properties of liquids and solids
• Liquids:

  • Interparticle attractive forces are strong enough to hold particles together but not strong enough to restrict movement
  • Capacity to flow
  • Can be poured and assume the shape of their containers
  • More dense and less compressible than gases
  • Definite volume independent of size and shape of container
• Solids:

  • Intermolecular forces between neighboring particles are strong enough to keep them locked in position
  • Not very compressible like liquids due to lack of space between particles
  • Highly ordered packing arrangement results in crystalline structures
• Kinetic energy:

  • Keeps molecules apart and in motion
  • Function of the substance's temperature
• Factors affecting the state of a substance:

  • Temperature: heating and cooling change the kinetic energy of particles, thus affecting the physical state
  • Pressure: increasing pressure increases the strength of intermolecular forces
• Kinetic Molecular Theory (KMT) explains the behavior of matter:

  • Matter is made of particles in constant motion (kinetic energy)
  • Amount of kinetic energy is directly proportional to temperature
  • Space between particles relates to the substance's state of matter
  • Phase changes occur with sufficient temperature changes
  • Stronger intermolecular forces cause particles to get closer together
• Properties of liquids:

  • Surface tension
  • Viscosity
  • Capillarity
  • Vapor pressure and boiling point
  • Molar heat of vaporization
• Surface tension:

  • Cohesive forces between liquid molecules
  • Strong cohesion results in difficulty moving objects through the surface
  • Small objects can "float" on the surface due to surface tension
• Viscosity:

  • Fluid's resistance to flow
  • Dynamic/absolute/simple viscosity and kinematic viscosity
• Capillarity:

  • Rise or depression of a liquid in a small passage
  • Result of surface/interfacial forces
• Vapor pressure and boiling point:

  • Vapor pressure: tendency of particles to escape from the liquid at a given temperature
  • Normal boiling point: temperature at which vapor pressure equals atmospheric pressure