| insoluble solid + liquid | filtration |
| dissolved solid (want solid) | evaporation / crystallisation |
| dissolved solid (want liquid) | simple distillation |
| miscible liquids | fractional distillation (b.p.) |
| dyes | paper chromatography |
| sand + salt | dissolve → filter → evaporate |
| iodine / NH₄Cl PURE | sublimation |
| pure | sharp, fixed m.p. & b.p. |
| impure | m.p. lower, b.p. higher, over a range |
| chromatogram | 1 spot = pure |
| Rf PURE | spot ÷ solvent front |
| accurate volume | burette, pipette |
| gas volume | gas syringe |
| density | ρ = m ÷ V (water 1 g/cm³) |
| solid | fixed, vibrate |
| liquid | close, slide past |
| gas | far apart, fast, random |
| melting/boiling | temp constant — energy overcomes forces |
| diffusion PURE | faster: hotter, lighter Mᵣ |
| proton | +1, mass 1, nucleus |
| neutron | 0, mass 1, nucleus |
| electron | −1, ~0, shells 2,8,8 |
| neutrons | A − Z |
| isotopes | same p, different n |
| outer e⁻ = group | shells = period |
| conc. H₂SO₄ | most gases, NOT NH₃ |
| CaO | NH₃ |
| fused CaCl₂ | most, NOT NH₃ |
| element | 1 type of atom |
| compound | chemically joined, fixed ratio, new properties |
| mixture | not joined, separate physically |
| Structure | M.p. | Conducts? | Example |
|---|---|---|---|
| giant ionic | high | molten / aq only | NaCl, MgCl₂ |
| simple molecular | low | never | H₂O, CO₂, CH₄, I₂ |
| giant covalent PURE | very high | no (graphite yes) | diamond, graphite, SiO₂ |
| metallic | high | solid + molten | Cu, Fe |
| +1 | Na⁺ K⁺ Ag⁺ H⁺ NH₄⁺ |
| +2 | Mg²⁺ Ca²⁺ Zn²⁺ Cu²⁺ Fe²⁺ Ba²⁺ |
| +3 | Al³⁺ Fe³⁺ |
| −1 | Cl⁻ Br⁻ I⁻ OH⁻ NO₃⁻ HCO₃⁻ |
| −2 | O²⁻ SO₄²⁻ CO₃²⁻ |
| −3 | PO₄³⁻ |
| formula | charges add to 0 |
| balance | big numbers only |
| diatomic | H₂ N₂ F₂ O₂ I₂ Cl₂ Br₂ |
| state symbols | (s) (l) (g) (aq) |
| ionic eqn | cancel spectator ions |
| alloys | brass Cu+Zn · stainless steel Fe+Cr |
| acid + metal | salt + H₂ |
| acid + carbonate | salt + H₂O + CO₂ |
| acid + base | salt + H₂O |
| base + NH₄⁺ salt | salt + H₂O + NH₃ |
| neutralisation | H⁺ + OH⁻ → H₂O |
| acid soil | add Ca(OH)₂ |
| UI | red (acid) · green 7 · violet (alkali) |
| methyl orange | red · orange · yellow |
| litmus | red in acid · blue in alkali |
| acidic oxide | non-metal (CO₂, SO₂, NO₂) |
| basic oxide | metal (CuO, MgO) |
| amphoteric | Al₂O₃, ZnO |
| neutral | CO, NO, H₂O |
| always soluble | Na⁺, K⁺, NH₄⁺, nitrates |
| insoluble chlorides | AgCl, PbCl₂ |
| insoluble sulfates | BaSO₄, PbSO₄, CaSO₄ |
| carbonates | only Na, K, NH₄ soluble |
| insoluble salt | precipitation → filter |
| soluble (not Na/K/NH₄) | excess solid + acid → filter |
| soluble Na/K/NH₄ | titration, repeat without indicator |
| strong vs weak acid | fully vs partly ionised |
| Ion | NaOH | excess NaOH | NH₃ | excess NH₃ |
|---|---|---|---|---|
| Cu²⁺ | light blue ppt | insol. | light blue ppt | dark blue soln |
| Fe²⁺ | green ppt | insol. | green ppt | insol. |
| Fe³⁺ | red-brown ppt | insol. | red-brown ppt | insol. |
| Zn²⁺ | white ppt | dissolves | white ppt | dissolves |
| Al³⁺ | white ppt | dissolves | white ppt | insol. |
| Ca²⁺ | white ppt | insol. | no ppt | — |
| NH₄⁺ | no ppt; warm → NH₃ |
| CO₃²⁻ | acid → effervescence, CO₂ |
| Cl⁻ | HNO₃ + AgNO₃ → white ppt |
| I⁻ PURE | HNO₃ + AgNO₃ → yellow ppt |
| SO₄²⁻ | HNO₃ + Ba(NO₃)₂ → white ppt |
| NO₃⁻ | NaOH + Al foil, warm → NH₃ |
| H₂ | lighted splint pops |
| O₂ | relights glowing splint |
| CO₂ | limewater white ppt |
| NH₃ | damp red litmus → blue |
| Cl₂ | bleaches damp litmus |
| SO₂ | acid. KMnO₄ purple → colourless |
| Cu²⁺(aq) | blue |
| Fe²⁺(aq) | pale green |
| Fe³⁺(aq) | yellow-brown |
| Cl₂ | yellow-green gas |
| Br₂ | red-brown liquid |
| I₂ | black solid, purple vapour |
| KMnO₄ | purple |
| KI(aq) → brown | unknown is an oxidising agent |
| acid. KMnO₄ purple → colourless | unknown is a reducing agent |
| n | m ÷ Mᵣ |
| gas n | V ÷ 24 (dm³, r.t.p.) |
| c | n ÷ V (dm³) |
| g/dm³ | mol/dm³ × Mᵣ |
| particles | n × 6.02 × 10²³ |
| cm³ → dm³ | ÷ 1000 |
| ratio | from balanced equation (moles!) |
| limiting reactant | runs out first |
| % yield PURE | actual ÷ theoretical × 100 |
| % purity PURE | pure ÷ sample × 100 |
| % element PURE | (no. × Aᵣ) ÷ Mᵣ × 100 |
| empirical PURE | % → ÷Aᵣ → ÷ smallest |
| Group 1 ↓ | more reactive, lower m.p., soft |
| Group 1 + water | alkali + H₂ |
| Group 17 ↓ | less reactive, darker, solid |
| displacement | more reactive halogen wins |
| Group 18 | full shell, unreactive, monatomic |
| across period | metal → non-metal |
| order | K Na Ca Mg Zn Fe Pb (H) Cu Ag |
| above carbon | extract by electrolysis |
| below carbon | reduce oxide with C |
| rusting | needs O₂ + water |
| prevent | paint, oil, plastic · galvanise, sacrificial PURE |
| transition PURE | coloured, variable ox. states, catalysts |
| oxidation | gain O · lose H · lose e⁻ · ox. state ↑ |
| reduction | lose O · gain H · gain e⁻ · ox. state ↓ |
| OIL RIG | oxidation is loss, reduction is gain |
| ox. states | element 0, O −2, H +1, sum = charge |
| exothermic | gives out heat, temp ↑ (ΔH −) |
| endothermic | takes in heat, temp ↓ (ΔH +) |
| bond breaking PURE | endothermic |
| bond making PURE | exothermic |
| concentration ↑ | more frequent collisions |
| pressure ↑ | particles closer |
| particle size ↓ | more surface area |
| temperature ↑ | more energetic + frequent |
| catalyst PURE | lower activation energy |
| cathode (−) | reduction · less reactive cation (H⁺ unless Cu²⁺/Ag⁺) |
| anode (+) | oxidation · O₂ unless conc. halide |
| purify Cu | impure Cu = anode |
| plating | object = cathode |
| Haber | N₂ + 3H₂ ⇌ 2NH₃ · 450 °C, 200 atm, Fe |
| Series | Formula | Group | Key reaction |
|---|---|---|---|
| alkanes | CₙH₂ₙ₊₂ | C–C only | combustion · Cl₂ substitution (UV) |
| alkenes | CₙH₂ₙ | C=C | bromine water orange → colourless · addition |
| alcohols | CₙH₂ₙ₊₁OH | –OH | fermentation · oxidise → acid |
| carboxylic acids | –COOH | –COOH | weak acid |
| esters PURE | acid + alcohol | –COO– | sweet smell, conc. H₂SO₄ |
| names | meth 1 · eth 2 · prop 3 · but 4 |
| cracking | big alkane → small alkane + alkene |
| addition polymer | C=C opens · poly(ethene) |
| condensation PURE | nylon, Terylene (lose H₂O) |
| biofuel | bioethanol (CO₂ balanced) |
| dry air | 78% N₂, 21% O₂, ~1% Ar, 0.04% CO₂ |
| CO | incomplete combustion · toxic |
| SO₂, NOₓ | acid rain |
| CO₂, CH₄ | greenhouse gases |
| cat. converter PURE | 2CO + 2NO → 2CO₂ + N₂ |
| ozone PURE | destroyed by CFCs |