A list of substances is shown.
aluminium oxide calcium oxide chlorine ethanol graphite nitrogen oxygen propane propene silicon(IV) oxide
Answer the questions using the list of substances. Each substance may be used once, more than once, or not at all.
State which of the substances:
Most-appropriate topic codes (Cambridge IGCSE Chemistry 0620):
• Topic 2.6 — Giant covalent structures (Part (a))
• Topic 11.1 — Formulae, functional groups and terminology (Parts (b), (g))
• Topic 7.2 — Oxides (Part (c))
• Topic 2.6 — Giant covalent structures (Part (d))
• Topic 2.5 — Simple molecules and covalent bonds (Part (e))
• Topic 9.6 — Extraction of metals (Part (f))
• Topic 11.6 — Alcohols (Part (h))
• Topic 10.3 — Air quality and climate (Part (i))
(a) silicon(IV) oxide
Silicon(IV) oxide ($\mathrm{SiO_2}$) has a structure where each silicon atom is bonded to four oxygen atoms and each oxygen atom to two silicon atoms, forming a continuous giant covalent lattice, similar to diamond.
(b) propene
Propene ($\mathrm{C_3H_6}$) contains a carbon-carbon double bond (C=C), making it an unsaturated hydrocarbon.
(c) aluminium oxide
Aluminium oxide ($\mathrm{Al_2O_3}$) reacts with both acids and bases, classifying it as an amphoteric oxide.
(d) graphite
Graphite contains delocalised electrons between its layers of carbon atoms, which can move freely and carry an electric current even in the solid state.
(e) ethanol OR propene
Ethanol ($\mathrm{C_2H_5OH}$) has 2 C, 6 H, and 1 O atom, totalling 9 atoms. Propene ($\mathrm{C_3H_6}$) also has 3 C and 6 H atoms, totalling 9 atoms in its simple molecular structure. (Mark scheme accepts either).
(f) silicon(IV) oxide and calcium oxide
In the blast furnace, calcium oxide ($\mathrm{CaO}$), formed from limestone, reacts with silicon(IV) oxide ($\mathrm{SiO_2}$), an impurity in the iron ore, to form molten slag (calcium silicate, $\mathrm{CaSiO_3}$).
(g) propane
Propane ($\mathrm{C_3H_8}$) fits the general formula $\mathrm{C}_n\mathrm{H}_{2n+2}$, which is the definition of the alkane homologous series.
(h) ethanol
Ethanol is manufactured industrially by the catalytic addition of steam (water) to ethene: $\mathrm{C_2H_4 + H_2O \rightarrow C_2H_5OH}$.
(i) nitrogen
Clean, dry air is composed of approximately $78\%$ nitrogen ($\mathrm{N_2}$) by volume.
