Chemistry I · for complete beginners
All lessons
Nine chapters plus a math warm-up. Every chapter is free to read here.
- Chapter 0: Math first: units, measurement, and matter
FreeConversion factors and unit cancellation · Metric prefixes: nano to mega · Solving for an unknown · Measurement: density, precision, and significant figures · Matter: elements, compounds, mixtures, and states · Changes, heat, and scientific methods
- Chapter 1: Atomic structure
FreeStart with the periodic table · Three particles with three different jobs · Mass number counts the nucleus · Neutral atoms and charged ions · Isotopes and weighted averages
- Chapter 2: Compounds: formulas and names
FreeRecognize the two compound types · Ion reference and predictable charges · Ionic formulas in both directions; subscripts and parentheses · Ionic names in both directions · Molecular formulas and names · Acids, strong bases, and mixed route practice
- Chapter 3: Electrons and periodic patterns
FreeShells, subshells, orbitals, and electrons · Writing an electron configuration · Light and atomic energy: what changes when an electron absorbs energy? · Reading the quantum labels · Using periodic trends with care · Periodic patterns: shielding, electron affinity, and successive ionization
- Chapter 4: The mole and chemical formulas
FreeA mole is a counting unit · Moving between grams and moles · Percent composition and empirical formulas · Finding the molecular formula
- Chapter 5: Stoichiometry and reaction amounts
FreeBalance equations before using the recipe · Five common reaction types · A balanced reaction is a recipe · Grams A ↔ moles A ↔ moles B ↔ grams B · The limiting reactant · Yield tells how close the result came
- Chapter 6: Solutions and aqueous reactions
FreeConcentration describes amount per volume · Dilution conserves the dissolved amount · What stays dissolved and what reacts · Acid–base reactions: see the particles in water · Solution stoichiometry and titration · Redox: electron transfer
- Chapter 7: Heat and enthalpy
FreeChoose the system before choosing a sign · Connecting heat to a temperature change · Scaling and combining reaction energies · Formation values and bond energies
- Chapter 8: Bonding and molecular properties
FreeLewis structures count outer electrons · Formal charge and resonance · Electron regions lead to molecular shape · Bonding models: hybridization, sigma/pi bonds, and bond order · Polarity and attractions between molecules · Alkanes and simple organic molecules
- Chapter 9: Gases and states of matter
FreePredict the direction before using a formula · Using the ideal gas equation · Partial pressure: each gas contributes to the total · Effusion: lighter gases escape faster (inside 9.3) · Phase changes use a different heat route
Final coming up?
Take the 70-question practice final
Modeled on standardized first-term general chemistry finals: 70 questions, 110 minutes. Timed or untimed. Full feedback on every question, plus your score by topic. The first 20 are free; the full final is $7.99 for 2 weeks.
Original ChemGem questions.