Overview
This lecture reviews core topics for the Chemistry Regents exam, covering concepts, calculations, models, and problem-solving skills necessary for success.
Matter & Mixtures
- Particle diagrams represent different states: molecules spread out in gases, closer in liquids.
- Sand can be separated from mixtures by filtration due to particle size.
- Solubility depends on temperature and is found using reference tables.
- Heterogeneous mixtures have non-uniform composition; homogeneous mixtures are uniform.
- The proportions of components in mixtures can vary.
Physical & Chemical Changes
- Sublimation is the direct phase change from solid to gas (e.g., dry ice).
- Heat flows from objects at higher temperature to those at lower temperature.
- Average kinetic energy increases with temperature.
Atomic Structure & Models
- Electrons absorb energy to move to higher levels and release energy as light when returning.
- Isotopes differ in the number of neutrons but have the same number of protons.
- The nucleus contains protons; atoms are mostly empty space.
- The periodic table organizes elements by atomic number and groups by valence electrons.
Chemical Bonding
- Ionic bonds form between metals and non-metals; covalent bonds between non-metals.
- Lewis dot diagrams show valence electrons.
- Nonpolar molecules have symmetrical charge distribution; polar molecules do not.
- The greater the electronegativity difference, the more polar the bond.
Chemical Formulas & Calculations
- Density = mass/volume.
- Percent composition = (mass of part / mass of whole) × 100%.
- Empirical formula is the simplest whole-number ratio of elements.
- Molarity = moles of solute / liters of solution.
Solutions & Solubility
- Solubility curves show how much solute dissolves at certain temperatures.
- Freezing point decreases with increased solute concentration (freezing point depression).
- Saturated, unsaturated, and supersaturated refer to solute amount in solution relative to capacity.
Thermochemistry & Kinetics
- Entropy measures disorder; gases have higher entropy than solids.
- Catalysts speed up reactions by lowering activation energy.
- Reaction rate increases with higher temperature, surface area, or concentration.
- Equilibrium requires a closed container; forward and reverse reaction rates are equal.
Acids, Bases & Titration
- Neutralization: acid + base → salt + water.
- pH less than 7 is acidic, greater than 7 is basic.
- Titration is used to determine concentration by neutralizing a known substance.
Gas Laws
- Ideal gases: behave ideally at high temperature and low pressure.
- Gas laws equations relate pressure, volume, and temperature changes.
Redox, Electrochemistry & Nuclear Chemistry
- Oxidation is loss, reduction is gain of electrons (OIL RIG).
- In a voltaic cell, electrons flow from anode to cathode.
- Fission releases more energy than chemical combustion.
- Isotopic notation shows mass and atomic number.
- Half-life measures time for half a radioactive sample to decay.
Organic Chemistry
- Alkanes have single bonds (CnH2n+2), alkenes double, alkynes triple.
- Isomers have the same molecular formula, different structures.
- Functional groups define classes (e.g., alcohols, esters).
- Addition reactions add atoms to double/triple bonds; saturated hydrocarbons have only single bonds.
Key Terms & Definitions
- Filtration — separation based on particle size.
- Sublimation — phase change directly from solid to gas.
- Isotope — atoms with same protons, different neutrons.
- Lewis Dot Diagram — shows valence electrons.
- Molarity — concentration in moles per liter.
- Catalyst — substance that speeds up a reaction.
- Titration — process to determine solution concentration.
- Entropy — measure of disorder.
- Oxidation — loss of electrons; Reduction — gain of electrons.
Action Items / Next Steps
- Practice problems in each unit using your reference table.
- Review key diagrams, equations, and definitions.
- Complete any assigned readings or worksheets as directed.