General chemistry 2

• General Chemistry 1 covers the basic concepts in chemistry, including the composition, structure, and properties of matter; quantitative principles, kinetics, and energetics of transformations of matter; and fundamental concepts of organic chemistry
• General Chemistry 2 explores intermolecular forces, thermochemistry, chemical kinetics, and acid-base and salt equilibria
• Matter can exist in three main states: solid, liquid, and gas
• The kinetic molecular theory explains that matter is composed of tiny particles in constant motion, and the state of a substance depends on the balance between kinetic energy and intermolecular forces
• Postulates of Kinetic Molecular Theory:

  • Matter is made of particles constantly in motion
  • The amount of kinetic energy is related to temperature
  • There is space between particles
  • Phase changes occur with temperature changes
  • Attractive intermolecular forces increase as particles get closer
• In liquids, molecules are close together with little empty space, making them difficult to compress and denser than gases. Liquids have a definite volume and can flow and be poured
• In solids, molecules are held rigidly in position with virtually no freedom of movement, making them almost incompressible with a definite shape and volume
• Intermolecular forces are attractive forces between molecules and are responsible for the non-ideal behavior of gases, exerting more influence in liquids and solids
• Types of Intermolecular Forces:

  • London dispersion forces
  • Dipole-dipole forces
  • Hydrogen bonding
  • Ion-dipole forces
• London dispersion forces are found in halogens, noble gases, and non-polar molecules, part of weak intermolecular attractions
• Dipole-dipole forces are attractive forces between polar molecules, based on Coulomb's law
• Hydrogen bonding is a strong dipole-dipole interaction in polar molecules containing hydrogen and highly electronegative elements like oxygen, nitrogen, or fluorine
• Ion-dipole forces act between an ion and a polar molecule, commonly observed when an ionic compound is placed in an aqueous solution
• Ion-dipole forces result from an electrostatic interaction between a charged ion and a molecule with a dipole
• Cations can attract the partially negative end of a neutral polar molecule, while anions attract the positive end of a polar molecule
• Ion-dipole interactions are involved in the dissolution process, such as sodium chloride (table salt) dissolving in water
• Ion-dipole forces are the strongest of the four intermolecular forces
• Hydrogen bonding is a special type of dipole-dipole interaction
• Dipole-dipole interactions are weaker than ion-dipole and hydrogen bonding
• London dispersion forces are the weakest intermolecular forces
• Surface tension is the force that causes the surface of a liquid to contract
• Surface tension allows a liquid to resist an external force due to the cohesive nature of its molecules
• Surface tension depends on the intermolecular force of attraction
• Water has high surface tension due to its ability to form hydrogen bonds
• Capillary action is the tendency of a liquid to rise in narrow tubes or be drawn into small openings
• Capillary action is a result of intermolecular attraction between the liquid and solid materials
• Cohesion is the intermolecular attraction between like molecules
• Adhesion is an attraction between unlike molecules
• Viscosity is the resistance of fluids to flow
• An increase in temperature decreases viscosity
• Viscosity is expressed in units of centipoise
• Vaporization is a phase change from liquid to gas
• Volatile substances have weak intermolecular forces of attraction
• Molar heat of vaporization is the energy required to vaporize 1 mole of a liquid at a given temperature
• The molar heat of vaporization is a measure of the strength of intermolecular forces in a liquid
• Acetone has a lower molar heat of vaporization than water
• The boiling point of a liquid is the temperature at which the liquid changes into a gas
• A liquid boils when its vapor pressure equals the pressure
• Boiling point of a liquid is the temperature at which it changes into a gas
• Liquid boils when its vapor pressure equals the pressure acting on its surface