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Chemistry Essentials – Long Summary

Introduction

  • Chemistry = study of matter (anything with mass & occupies space) and energy, plus the changes they undergo
  • Hardly any human activity is chemistry‐free; cleaners, medicines, fuels, metallurgy, food & drink all depend on it
  • Book’s scope ➜ “bare essentials” of a first-semester HS/college general-chem course; detailed, example-rich, light on fluff
  • Reminder: italicised words introduce new terms; bold text highlights key steps in lists
  • Foolish assumptions (why you might use these notes): exam review, professional test prep, parental homework help, “non-traditional” student refresher

Matter & Energy (Ch. 1)

  • States of matter
    • Solids: definite shape/volume, particles in rigid crystal lattice, vibrate only slightly
    • Liquids: definite volume, no fixed shape, particles farther apart & mobile; may form small clusters
    • Gases: no fixed shape/volume; particles far apart, independent, fill container
  • Phase changes
    • Condensation (gas→liquid); Freezing (liquid→solid),
      \text{H}2\text O(g)→\text{H}2\text O(l)→\text{H}_2\text O(s)
    • Melting & boiling: at mp & bp T remains constant until change complete; melting point = freezing point
    • Sublimation/deposition: solid⇌gas (dry ice, mothballs)
  • Pure substances vs. mixtures
    • Pure: elements & compounds (constant composition)
    • Mixtures: homogeneous (solutions) vs. heterogeneous; can separate by physical means
  • Measurements & SI
    • Length-m, mass-g (kg), volume-L; prefixes: k=10^3, c=10^-2, m=10^-3
  • Physical vs. chemical properties
    • Extensive (mass, V) vs. intensive (color, density d=\frac m v)
  • Energy
    • Kinetic (motion) vs. potential (stored in position/bonds); law of conservation of energy
    • Temperature = avg kinetic energy; units °C, K (K=°C+273); heat unit joule (J), 1\;\text{cal}=4.184\;\text J

Atomic Structure (Ch. 2)

  • Sub-atomic particles
    • Proton p^+ (mass≈1 amu, +1), neutron n^0 (≈1 amu, 0), electron e^- (0.0005 amu, −1)
  • Nucleus: dense 10⁻¹⁵ m core; A=Z+N (mass #); element notation ^A_ZX
  • Isotopes & ions
    • Isotopes: same Z, different N (e.g. ^11H, ^21H, ^3_1H); average atomic mass on PT is weighted by abundance
    • Ions: loss ⇒ cation, gain ⇒ anion (Na→Na⁺, Cl→Cl⁻)
  • Quantum model
    • 4 quantum #’s: n,l,ml,ms; subshell letters s,p,d,f
    • Aufbau filling order (1s < 2s < 2p < 3s < 3p < 4s < 3d …); Hund’s rule; Pauli exclusion (↑↓)
  • Electron configuration (O: 1s^22s^22p^4); valence = outer s,p e⁻ ⇒ governs chemistry

Periodic Table (Ch. 3)

  • Arranged by increasing Z; rows=periods (7); columns=groups/families (IA etc or 1–18)
  • Classifications
    • Metals (left of staircase): shiny, conductive, malleable, form cations
    • Non-metals (right): brittle, insulators, form anions
    • Metalloids (B, Si, Ge, As, Sb, Te, At): semi-conductors
  • Representative trends: valence = group number (A-families) ⇒ predictable ionic charges

Nuclear Chemistry (Ch. 4)

  • Natural decay modes
    • α (^42He), β (^0{-1}e), γ (energy), positron ^0_{+1}e, electron capture
  • Balancing nuclear eqn: conserve A & Z (e.g. ^{35}{17}Cl+^10n→^{1}{1}H+^{35}{16}S)
  • Half-life t{1/2}: N=N0e^{-kt}; C-14 dating; U-238 decay series
  • Fission: U-235 or Pu-239 + n → lighter nuclei + energy; mass defect E=mc^2; chain reaction, critical mass
  • Fusion: light nuclei (H-2+H-3) → He-4 + n + energy; powers Sun

Ionic Bonding (Ch. 5)

  • Atoms gain/lose e⁻ to satisfy octet (noble gas config)
  • Charges from PT: IA +1, IIA +2, IIIA +3, VA −3, VIA −2, VIIA −1; transition metals → multiple ox states (Fe²⁺/Fe³⁺)
  • Polyatomic ions (must memorise): \text{SO}4^{2-},\text{NO}3^-,\text{OH}^-,\text{NH}_4^+,…
  • Formula prediction: criss-cross; Na⁺ + Cl⁻ → NaCl; Mg²⁺ + Br⁻ → MgBr₂
  • Naming
    • Metal (roman numeral) + nonmetal-ide (CuCl₂ = copper(II) chloride)
    • Polyatomic stays intact (NH₄)₂SO₄ = ammonium sulfate
  • Electrolytes conduct (ionic), nonelectrolytes don’t (covalent)

Covalent Bonding (Ch. 6)

  • Atoms share e⁻ pairs to fill valence shells; single/double/triple bonds; \text N_2 has triple
  • Representations
    • Lewis structures (dots/dashes), electron-dot, condensed
  • Bond polarity & EN
    • \Delta EN
    • Polar bonds ⇒ molecular dipoles ⇒ H-bonding (O–H,N–H,F–H)

Chemical Reactions (Ch. 7)

  • Types
    • Combination, Decomposition, Single- & Double-Displacement (precipitation/neutralisation), Combustion, Redox
  • Collision theory: proper orientation + sufficient E_a ⇒ reaction
  • Energy diagrams; exothermic (heat product) vs endothermic
  • Balancing: adjust coefficients to satisfy law of mass conservation (e.g. \text{C}4\text H{10}+13O2→8CO2+10H_2O)
  • Equilibrium K_{eq}=\frac{[products]}{[reactants]}
    • Le Chatelier: stress by \Delta[conc], \Delta T, \Delta P shifts position
  • Kinetics: rate ↑ with T, [reactants], catalysts; activation energy lowered by catalysts (hetero/homo)

Electrochemistry (Ch. 8)

  • Redox basics
    • Oxidation = e⁻ loss; reduction = e⁻ gain; LEO goes GER
    • \text{Zn}→\text{Zn}^{2+}+2e^-, \text{Cu}^{2+}+2e^-→\text{Cu}
  • Balancing redox (acidic): split into half-rxns, balance O with \text H_2\text O, H with \text H^+, add e^-, equalise e^-, combine
  • Galvanic (voltaic) cells: spontaneous redox → electricity; anode(−) oxidation, cathode(+) reduction; Daniell Zn/Cu cell ~1.1 V
  • Electrolytic cells: electricity drives non-spontaneous redox; electroplating, water electrolysis 2H2O→2H2+O_2
  • Rechargeables: Pb storage battery: discharge \text{Pb}+\text{PbO}2+2H2SO4→2PbSO4+2H_2O, reverse when charging

The Mole & Stoichiometry (Ch. 9)

  • 1\text{ mol}=6.022\times10^{23} particles (Avogadro)
  • Gram–mole link: grams ÷ molar mass ⇒ mol; mol × molar mass ⇒ grams
  • Empirical vs molecular formulas; percentage → empirical → molecular
  • Reaction stoichiometry: coefficients = mole ratios; limiting reagent, theoretical & % yield \%\text{yield}=\frac{actual}{theoretical}×100

Solutions & Concentrations (Ch. 10)

  • Terminology: solvent (largest), solute(s)
  • Solubility g/100 mL varies with T; saturated/unsaturated/supersaturated
  • Units
    • % (w/w, w/v, v/v), ppm/ppb, M=\frac{mol\,solute}{L\,solution}, m=\frac{mol\,solute}{kg\,solvent}
  • Dilution M1V1=M2V2
  • Colligative props: ⬆ boiling-point, ⬇ freezing-point proportional to molality; osmotic pressure

Acids & Bases (Ch. 11)

  • Brønsted–Lowry: acid = H^+ donor; base = H^+ acceptor; conjugate acid-base pairs
  • Strong: complete ionisation (HCl, HBr, HI, HNO3,HClO4,H2SO4 1st); strong bases (IA, IIA hydroxides)
  • Weak: partial ionisation; Ka,Kb equilibrium constants (acetic acid K_a=1.8×10^{-5})
  • Water auto-ionisation Kw=[H3O^+][OH^-]=1.0×10^{-14}
  • pH =−\log[H_3O^+]; pH+pOH=14; indicators: litmus (red acid/blue base), phenolphthalein (acid clear/base pink)
  • Titrations: neutralisation stoichiometry → unknown M determination

Gases & Gas Laws (Ch. 12)

  • Kinetic Molecular Theory: gas particles tiny, far apart, continuous random motion, elastic collisions, negligible forces, T\propto KE_{avg}
  • Laws
    • Boyle PV=k ((P1V1=P2V2))
    • Charles V/T=k, Gay-Lussac P/T=k, combined \frac{P1V1}{T1}=\frac{P2V2}{T2}
    • Avogadro V/n=k; 1 mol gas at STP ⇒ 22.4 L
    • Ideal gas law PV=nRT with R=0.0821\;L·atm·K^{-1}·mol^{-1}

Nuclear & Industrial “Happy Accidents” (Ch. 13)

  • Archimedes’ density test ➜ Eureka principle
  • Goodyear’s hot rubber + S ➜ vulcanised rubber
  • Pasteur’s tartaric enantiomers ➜ molecular chirality
  • Perkin’s black gunk ➜ fi rst synthetic dye (mauve)
  • Kekulé’s dream ➜ benzene ring
  • Becquerel’s fogged plate ➜ radioactivity
  • Plunkett’s clogged TFE tank ➜ Tefl on®
  • 3M’s weak glue ➜ Post-it® note
  • Minoxidil side-effect ➜ hair-growth drug
  • Saccharin & aspartame ➜ accidental sweeteners

Key Equations to Remember

  • d=\frac m v (density)  q=m·c·ΔT (heat)  PV=nRT (ideal gas)
  • t_{1/2}=\frac{0.693}{k} (1st-order decay)  E=mc^2 (mass–energy)
  • Kw=1.0×10^{-14}=10^{-pH}·10^{-pOH}  pH=-\log[H3O^+]
  • Stoichiometry roadmap: g ↔ mol ↔ mol ↔ g

“Like-dissolves-like, opposites attract, and electrons do all the work.”