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Unit 3: Intermolecular Forces and Properties

13 dot points across 13 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How does the Beer-Lambert law let us find the concentration of a colored solution from how much light it absorbs?

Topic 3.13 Beer-Lambert Law: use the Beer-Lambert law to relate the absorbance of a solution to its concentration, and apply a calibration to find an unknown concentration.
A focused answer to AP Chemistry Topic 3.13, covering the Beer-Lambert law A equals epsilon b c, the meaning of absorbance, molar absorptivity and path length, and how a calibration curve determines an unknown concentration, with full worked examples.
9 min answer →

Why do real gases deviate from ideal behavior, and under what conditions is the deviation greatest?

Topic 3.6 Deviation from Ideal Gas Law: explain why real gases deviate from the ideal gas law at high pressure and low temperature in terms of molecular volume and intermolecular forces.
A focused answer to AP Chemistry Topic 3.6, covering why real gases depart from PV equals nRT, the roles of finite molecular volume and intermolecular attractions, and the conditions (high pressure, low temperature) where deviations matter, with full worked examples.
9 min answer →

How does the ideal gas law relate the pressure, volume, temperature and amount of a gas?

Topic 3.4 Ideal Gas Law: use the ideal gas law and its partial-pressure and gas-density forms to relate the pressure, volume, temperature and amount of a gas in calculations.
A focused answer to AP Chemistry Topic 3.4, covering the ideal gas law PV equals nRT, the combined gas law, partial pressures and Dalton's law, mole fractions and gas density, with full worked examples.
10 min answer →

What forces act between molecules, and how do their relative strengths set a substance's physical properties?

Topic 3.1 Intermolecular Forces: identify and rank the intermolecular forces (London dispersion, dipole-dipole, hydrogen bonding, ion-dipole) present in a substance and relate their strength to properties such as boiling point and vapor pressure.
A focused answer to AP Chemistry Topic 3.1, covering London dispersion, dipole-dipole, hydrogen bonding and ion-dipole forces, how to rank their strength, and how intermolecular forces set boiling point, viscosity and vapor pressure, with full worked examples.
10 min answer →

What assumptions of kinetic molecular theory explain the behavior of an ideal gas and the shape of its speed distribution?

Topic 3.5 Kinetic Molecular Theory: state the postulates of kinetic molecular theory and use them to explain gas pressure, temperature, and the Maxwell-Boltzmann distribution of molecular speeds.
A focused answer to AP Chemistry Topic 3.5, covering the postulates of kinetic molecular theory, how they explain pressure and temperature, the link between average kinetic energy and temperature, and the Maxwell-Boltzmann speed distribution, with full worked examples.
9 min answer →

How does the photoelectric effect show that light is quantised into photons of energy proportional to frequency?

Topic 3.12 Photoelectric Effect: explain how the photoelectric effect demonstrates that light is quantised, using the threshold frequency and the relationship between photon energy and frequency.
A focused answer to AP Chemistry Topic 3.12, covering the photoelectric effect, the threshold frequency, why light below threshold ejects no electrons regardless of intensity, and how the effect establishes the photon model of light, with full worked examples.
9 min answer →

How does the type of particle and force in a solid determine its hardness, melting point and conductivity?

Topic 3.2 Properties of Solids: relate the macroscopic properties of a solid (melting point, hardness, conductivity) to its type (ionic, metallic, covalent network, molecular) and the forces holding its particles together.
A focused answer to AP Chemistry Topic 3.2, covering the four types of solid (ionic, metallic, covalent network, molecular), the forces in each, and how those forces explain melting point, hardness, brittleness and conductivity, with full worked examples.
9 min answer →

How do particulate diagrams represent the species actually present in a solution?

Topic 3.8 Representations of Solutions: use particulate-level diagrams to represent the species present in a solution, distinguishing strong electrolytes, weak electrolytes and nonelectrolytes.
A focused answer to AP Chemistry Topic 3.8, covering how to draw and interpret particulate diagrams of solutions, the difference between strong and weak electrolytes and nonelectrolytes, and how dissociation determines the species present, with full worked examples.
9 min answer →

How do separation techniques such as chromatography and distillation exploit differences in intermolecular forces?

Topic 3.9 Separation of Solutions and Mixtures (Chromatography): explain how chromatography, distillation and filtration separate the components of a mixture by exploiting differences in their interactions and properties.
A focused answer to AP Chemistry Topic 3.9, covering chromatography (stationary and mobile phases, relative affinities), distillation by boiling point and filtration by particle size, all explained through intermolecular forces, with full worked examples.
9 min answer →

How do the spacing, motion and forces of particles differ across the solid, liquid and gas states?

Topic 3.3 Solids, Liquids, and Gases: describe the particle-level differences between the three states and explain how intermolecular forces and temperature determine which state a substance is in.
A focused answer to AP Chemistry Topic 3.3, covering the particulate model of the three states, how intermolecular forces and kinetic energy compete to set the state, and how to read particulate diagrams and heating curves, with full worked examples.
9 min answer →

Why does a substance dissolve in one solvent but not another, and how do temperature and pressure affect solubility?

Topic 3.10 Solubility: explain solubility in terms of the intermolecular forces between solute and solvent (like dissolves like), and describe how temperature and pressure affect the solubility of solids and gases.
A focused answer to AP Chemistry Topic 3.10, covering the like dissolves like principle, solute-solvent intermolecular forces, the role of ion-dipole and hydrogen bonding, and how temperature and pressure shift solubility, with full worked examples.
9 min answer →

How do we describe the composition of a solution quantitatively using molarity?

Topic 3.7 Solutions and Mixtures: define solute, solvent and solution, and calculate and use molarity to relate moles, volume and concentration, including dilutions.
A focused answer to AP Chemistry Topic 3.7, covering solute and solvent, the molarity concentration formula, preparing solutions, and dilution calculations with the M1V1 equals M2V2 relationship, with full worked examples.
9 min answer →

How does the energy of electromagnetic radiation relate to its frequency, and which molecular transitions does each region of the spectrum probe?

Topic 3.11 Spectroscopy and the Electromagnetic Spectrum: relate the energy, frequency and wavelength of electromagnetic radiation and identify which type of molecular transition (rotational, vibrational, electronic) each region of the spectrum probes.
A focused answer to AP Chemistry Topic 3.11, covering the energy-frequency-wavelength relationships of light, the regions of the electromagnetic spectrum, and which molecular transition (rotational, vibrational, electronic) each region excites, with full worked examples.
9 min answer →