Chemical Patterns

"How are atoms held together in metals?"

"By metallic bonding - delocalised outer shell electrons move freely, forming strong metallic bonds"

"What is the structure of metals?"

"Giant structures of atoms arranged in a regular pattern with delocalised electrons"

"Why do metals have high melting and boiling points?"

"Strong metallic bonds require lots of energy to break"

"Why can metals conduct heat and electricity?"

"Because delocalised electrons move freely through the structure"

"Why can metals be bent and shaped?"

"Layers of atoms can slide over each other"

"What happens during electrolysis?"

"Positive ions move to the cathode (reduction), negative ions move to the anode (oxidation), producing elements"

"In molten ionic compounds

how do you predict electrolysis products?","Positive ions → cathode; Negative ions → anode"

"In electrolysis with inert electrodes

what is formed at the cathode and anode?","Cathode: metal or hydrogen; Anode: non-metal"

"What is an example of a half equation at the cathode?"

"X⁺ + e⁻ → X (reduction)"

"What is an example of a half equation at the anode?"

"X⁻ → X + e⁻ (oxidation)"

"What does OIL RIG stand for?"

"Oxidation Is Loss (of electrons), Reduction Is Gain (of electrons)"

"In electrolysis

what happens at the anode and cathode?","Anode = oxidation (loss, anions), Cathode = reduction (gain, cations)"

"Why is aluminium extracted by electrolysis?"

"It is too reactive to be reduced by carbon"

"How is aluminium extracted?"

"Electrolysis of molten aluminium oxide mixed with cryolite, using carbon anodes"

"Why is electrolysis expensive?"

"Large amounts of energy needed to melt compounds and produce current"

"In electrolysis of aqueous ionic solutions

what is produced at the cathode?","Hydrogen, unless the metal ion is less reactive than hydrogen (then the metal forms)"

"In electrolysis of aqueous ionic solutions

what is produced at the anode?","Oxygen (from OH⁻ in water), unless halide ions are present → then halogen forms"

"What are the products of electrolysis of copper chloride solution?"

"Cathode: Cu(s); Anode: Cl₂(g)"

"What are the products of electrolysis of sodium chloride solution?"

"Cathode: H₂(g); Anode: Cl₂(g)"

"Why is crude oil important?"

"It is a main source of hydrocarbons and a feedstock for the petrochemical industry"

"Why is crude oil finite?"

"It is a non-renewable resource, formed over millions of years, used faster than it is replaced"

"Give uses of crude oil fractions"

"Refinery gas → bottled gas; Gasoline → car fuel; Naphtha → chemicals; Kerosene → jet fuel; Diesel → engines; Fuel oil → ships/heating; Lubricating fraction → waxes/polish; Bitumen → roads"

"How is crude oil separated?"

"By fractional distillation - heated, vapours rise up column and condense at different levels"

"Why do long-chain hydrocarbons condense at the bottom of the column?"

"They have high boiling points due to stronger intermolecular forces"

"What series do crude oil fractions mainly belong to?"

"Alkanes (CnH₂n+₂)"

"Why do boiling points of hydrocarbons increase with chain length?"

"More intermolecular forces → more energy needed to break"

"How do you calculate empirical formula?"

"Find simplest whole number ratio of atoms (e.g. Fe₄O₆ → Fe₂O₃)"

"What type of bonding do simple molecules have?"

"Covalent bonding between non-metals"

"What is covalent bonding?"

"Sharing of outer shell electrons between atoms to gain full shells"

"What are the limitations of dot-and-cross diagrams?"

"Show bonding and electrons but not 3D arrangement"

"What are the limitations of ball-and-stick models?"

"Show 3D structure but not electrons or symbols"

"What do all models fail to show?"

"Intermolecular forces (the ones broken on melting/boiling)"

"Why do simple molecular substances have low melting/boiling points?"

"Weak intermolecular forces are easily broken"

"Why can't simple molecules conduct electricity?"

"No charged particles to carry current"

"What is cracking?"

"Breaking large hydrocarbons into smaller, useful ones by heating with a catalyst or steam"

"What are the products of cracking?"

"Smaller alkanes, alkenes, and sometimes hydrogen"

"What are the first 4 prefixes in organic chemistry?"

"Meth-, Eth-, Prop-, But- (Monkeys Eat Peanut Butter)"

"What is the suffix for alkanes

alkenes, alcohols, carboxylic acids?","-ane (alkanes), -ene (alkenes), -ol (alcohols), -anoic acid (carboxylic acids)"

"What is the general formula of alkanes?"

"CnH₂n+₂"

"What is the general formula of alkenes?"

"CnH₂n"

"What is the functional group of alcohols?"

"-OH"

"What is the functional group of carboxylic acids?"

"-COOH"

"What colour change is seen when bromine reacts with alkenes?"

"Orange → colourless (test for C=C bond)"

"What happens when alkenes react with hydrogen?"

"They form alkanes (addition reaction)"

"How are alcohols oxidised to carboxylic acids?"

"Using potassium manganate(VII), with orange → green colour change (reflux)"

"What determines reactions of organic compounds?"

"The generality of reactions of their functional groups"