Unit 3 AP Chem Video Notes

Page 1:

• Intermolecular forces:

  • Intramolecular forces: covalent bonds formed within a molecule

  • Intermolecular forces: forces between molecules

• Types of intermolecular forces:

  • Polar covalent bonds: formed due to polar molecules, electrostatic forces

  • Dipole-Dipole interactions: between any two polar molecules, attractive or repulsive

  • London Dispersion forces: interactions between nonpolar molecules, induced dipole

• Fish breathe O2 dissolved in polar water

  • Water attracts O2 molecules due to electrostatic forces

  • Interaction between nonpolar molecules also occurs due to fluctuations in electron distribution

Page 2:

• Comparing IMF strengths:

  • Boiling point and surface area are related

  • Higher boiling point indicates stronger intermolecular forces

• Lewis diagrams of ethane and methanal

  • Predict which one is a liquid at room temperature

  • Methanal is a liquid due to stronger London Dispersion forces caused by more electrons

Page 3:

• Hydrogen bonding and ion-dipole forces

  • Hydrogen compounds of group 16 have bent shape

  • Higher molar mass leads to more polarizable electron clouds and stronger London Dispersion forces

  • Water has high boiling point due to hydrogen bonding

• Interaction between ions and dipole

  • Charged ions in water cause separation and attraction between ions and water molecules

Page 4:

• Difference in boiling points of two substances

  • Ethanol has a higher boiling point due to the ability to form hydrogen bonds

  • Dimethyl ether cannot form hydrogen bonds

• Properties of substances explained by intermolecular forces

  • Melting and boiling point, vapor pressure, volatility, surface tension, viscosity, heat of vaporization

Page 5:

• Partial pressure and mole fraction of gas B

• Example problem with sealed containers and pressure

• Effect of temperature on kinetic energy

Page 6:

• Relationship between intermolecular forces and vapor pressure

• Comparison of different types of intermolecular forces

• Comparison of molecular structures and boiling points

Page 7:

• Explanation of boiling points of CS2 and COS

• CS2 has higher boiling point due to more electrons and stronger intermolecular forces

Page 8:

• Properties of solids

• Types of solids: ionic, molecular, metallic, network covalent

• Ionic solids have high melting and boiling points, but are brittle

• Molecular solids have weak intermolecular forces and relatively low melting and boiling points

Page 9:

• Covalent network solids and poor conductors

• Metalliods and their properties

• Metallic elements and their properties

Page 10:

• Phases of matter and their characteristics

• Vibrational and translational degrees of freedom

• Ideal Gas Law and its variables

Page 11:

• Effect of number of moles and temperature on pressure

Page 12:

• Effect of temperature on pressure

Page 13:

• Ideal gas law combines all organizers

• R = ideal gas constant, R = 0.08206 L-AM ad.k

• Gas Variable Relationships:

  • Pressure decreases when volume increases

  • Temperature decreases when volume increases

  • Number of moles decreases when volume decreases

• Examples:

  1. A gas with a pressure of 6.0 atm is reduced to 3.0 atm, temperature decreases, volume increases

  2. Balloon filled with air, taken outside on a cold day, temperature decreases, volume decreases

  3. Gas in piston compressed, volume decreases, temperature increases, pressure increases

Page 15:

• Kinetic Molecular Theory view:

  • Particles in continuous random motion

  • Collisions between particles result in new velocities and directions

  • Elastic collisions

  • Kelvin temperature is proportional to average kinetic energy

• Ideal gases:

  • Volume is negligible

  • Pressure is caused by particle collisions

  • Constant temperature means constant average kinetic energy

Page 16:

• Distribution of particle speeds:

  • Faster particles on the right side of the curve, slower particles on the left side

  • Area under the curve represents the number of particles

  • Different masses have different curves

  • Heavier particles are slower, represented by the curve on the left

Page 17:

• Deviation from ideal gas behavior:

  • Ideal case: no attractive or repulsive forces, volume is negligible

  • All gases can condense, have attractive forces, vary in size, and have volume

  • Effects of intermolecular forces (IMF):

    • As IMF increases, actual pressure becomes smaller than predicted

    • High temperature makes IMF negligible

  • Effects of volume:

    • Ideal gas law assumes no volume, but in reality, volume affects pressure

    • At low pressures, volume has a greater effect on pressure

Page 18:

• Non-ideal gases:

  • Low temperature, high pressures, significant IMFs or particle volume

  • HF behaves least ideally due to strong IMFs

Page 22:

• Separation of solutions:

  • Filtration can separate components of a liquid mixture

  • Chromatography separates components based on polarity differences

  • More polar components travel less on the paper or column

Page 23:

• Example of separation using chromatography:

  • Red dye and blue dye spots on a nonpolar mobile phase

  • Red dye travels farthest due to less IMF interactions

• Distillation:

  • Separates chemical species based on differential strength of IMFs

  • Effects of vapor pressure of mixture components

Page 25:

• Solubility:

  • Like dissolves like

  • Polar substances dissolve in polar solvents, nonpolar substances dissolve in nonpolar solvents

• Example:

  • SaH is least soluble in water

Page 28:

• Absorption of light:

  • N2 does not absorb visible light, but I2 absorbs UV and visible light

  • Visible light can promote electrons to higher energy levels

Page 33:

• Measurement of CuSo4 solution:

  • Use a buret to measure 37.5 mL of 0.400M CuSo4 solution

  • Fill the flask with water until the 100mL mark is reached

  • Minimize interference from Co2+ by using a wavelength of ~700nm, as Co2