Overview
This lecture provides a comprehensive review of all major Chemistry Regents exam topics, including matter, atomic structure, bonding, reactions, stoichiometry, solutions, energy, kinetics, equilibrium, acids/bases, organic chemistry, redox and electrochemistry, nuclear chemistry, and key calculations.
Matter and Particle Models
- Nitrogen gas (N₂) is represented by paired circles spaced far apart; in liquid, molecules are close together.
- Sand can be separated from mixtures by filtration due to larger particle size.
- Mixtures can be homogeneous (uniform) or heterogeneous (non-uniform, e.g., sand in water).
- The proportions of components in a mixture can vary, as shown in different mass values.
Phase Changes and Energy
- Sublimation is the direct phase change from solid to gas (e.g., dry ice).
- Heat flows from higher to lower temperature (air to dry ice).
- The increase in water temperature results from heat transfer from surroundings to the water.
- Average kinetic energy of molecules increases as temperature rises.
Atomic Structure and Spectra
- Electrons absorb energy to move to higher levels and release light when returning to lower levels.
- The electron configuration determines unique spectral lines, independent of element mass.
- Isotopes have the same number of protons but different numbers of neutrons.
Models of the Atom
- Both Bohr and Thomson models describe electrons as subatomic particles.
- Rutherford’s gold foil experiment concluded atoms are mostly empty space and have a positively charged nucleus.
- Protons are positively charged particles located in the nucleus.
Periodic Table and Trends
- Noble gases (Group 18) are stable and rarely form compounds due to filled valence shells.
- Atomic radius increases down a group as the number of electron shells increases.
- Metalloids (e.g., silicon) have properties between metals and nonmetals.
Chemical Bonding
- Ionic bonds form between metals and nonmetals (e.g., KBr, K₂O).
- Covalent bonds form between nonmetals; electron dot diagrams represent shared electrons.
- Polar molecules have unequal charge distribution; nonpolar molecules are symmetrical.
Solutions and Concentrations
- Solution concentration (molarity, M) is moles of solute per liter of solution.
- "Like dissolves like": polar substances dissolve in polar solvents.
- Freezing point decreases (depression) as solute concentration increases.
Stoichiometry and Calculations
- Use percent composition (part/whole × 100) for elements in compounds.
- Mass-mole relationships use molar mass (g/mol) for conversions.
- Empirical formula is the simplest whole-number ratio of elements.
Gases and Gas Laws
- Gases behave more ideally at high temperature and low pressure.
- Equal volumes of gases at the same T and P contain equal numbers of molecules (Avogadro’s law).
- Boyle’s, Charles’s, and combined gas law equations relate P, V, and T of gases.
Kinetics and Equilibrium
- Catalysts speed up reactions by lowering activation energy, not changing reactant/product energy.
- Rate of reaction increases with temperature, concentration, or surface area.
- At equilibrium, the rate of the forward and reverse reactions is equal.
- Increasing pressure shifts equilibrium toward the side with fewer gas moles.
Acids, Bases, and Titration
- pH < 7 is acidic, pH > 7 is basic; a change of 1 in pH equals a 10× change in [H⁺].
- Titration uses the formula: (M₁)(V₁) = (M₂)(V₂) to find unknown concentration.
- Neutralization produces water and a salt (acid + base → salt + H₂O).
Organic Chemistry
- Alkanes, alkenes, and alkynes are hydrocarbons with single, double, and triple bonds, respectively.
- Isomers have the same molecular formula but different structures.
- Alcohols contain -OH; esters have -COO- functional groups.
Redox and Electrochemistry
- Oxidation is loss of electrons; reduction is gain of electrons (OIL RIG).
- In voltaic cells, electrons flow from anode to cathode; oxidation occurs at the anode.
- Electrolytic cells require a power source (battery).
Nuclear Chemistry
- Fission releases much more energy than chemical reactions.
- Alpha (α), beta (β), and gamma (γ) are common decay modes; gamma has the strongest penetration.
- Half-life: time for half a radioactive sample to decay.
- The number of neutrons = mass number – atomic number.
Key Terms & Definitions
- Filtration — separating substances based on particle size.
- Sublimation — phase change from solid to gas.
- Spectral Lines — light emitted as electrons drop energy levels.
- Isotope — atoms with same protons, different neutrons.
- Catalyst — substance that lowers activation energy.
- Empirical Formula — simplest ratio of elements in a compound.
- Molarity (M) — moles of solute per liter solution.
- Voltaic Cell — electrochemical cell generating electricity from spontaneous redox reactions.
- Half-life — time for half a radioactive isotope to decay.
Action Items / Next Steps
- Practice additional Regents-style problems for each unit.
- Use the reference tables during practice and review.
- Review key formulas: gas laws, percent composition, molarity, and titration.
- Study definitions and structures for functional groups in organic chemistry.