Contents

States of matter

Atoms, elements and compounds

Stoichiometry

Electrochemistry

ElectrolysisBeing prepared
Electrolysis of solutions and electroplatingBeing prepared
Fuel cellsBeing prepared

Chemical energetics

Chemical reactions

Acids, bases and salts

Acids, bases and indicators
OxidesBeing prepared
Making saltsBeing prepared

The Periodic Table

Reading the tableBeing prepared
Group I: the alkali metalsBeing prepared
Group VII: the halogensBeing prepared
Transition elements and noble gasesBeing prepared

Metals

Metals and alloysBeing prepared
The reactivity seriesBeing prepared
CorrosionBeing prepared
Extracting metalsBeing prepared

Chemistry of the environment

WaterBeing prepared
FertilisersBeing prepared
Air quality and climateBeing prepared

Organic chemistry

Naming organic moleculesBeing prepared
Crude oil and alkanesBeing prepared
AlkenesBeing prepared
Alcohols and carboxylic acidsBeing prepared
PolymersBeing prepared

Experimental techniques and chemical analysis

Mixtures and separation
Measuring and planning experimentsBeing prepared
Crystallisation
Distillation
Paper chromatography
Choosing methods and checking purityBeing prepared
TitrationBeing prepared
Gas testsBeing prepared
Anion testsBeing prepared
Cation and flame testsBeing prepared

Part 2 of 2

Page 02

Molecules that melt easily

identify

Try it yourself

The table gives data for four substances. Which are likely to be simple molecular substances? Choose all that apply.

identify: name or select.

Substance	Melting point / °C	Boiling point / °C	Conducts as a solid?	Conducts as a liquid?
W	−95	69	no	no
X	734	1435	no	yes
Y	44	280	no	no
Z	1085	2562	yes	yes

Choose all statements you think are correcta.Xb.Wc.Zd.Y

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Scope and sources

Cambridge IGCSE Chemistry 0620 · 2026–2028 v2 · Original learning materials.

Simple molecules and covalent bonds (2.5 Core 1–3, Supplement 4–5): the covalent bond as a shared pair of electrons that gives noble-gas electronic configurations, dot-and-cross diagrams for H₂, Cl₂, H₂O, CH₄, NH₃ and HCl and, in the Supplement, CH₃OH, C₂H₄, O₂, CO₂ and N₂, and the low melting and boiling points and poor electrical conductivity of simple molecular compounds, explained in the Supplement by weak intermolecular forces and no moving charged particles. Giant covalent structures (2.6), metallic bonding (2.7) and formulae (3.1) have their own modules; the shapes of molecules are not in the syllabus.

Apparatus, amounts and times in the experiment are illustrative. Real practical work follows a teacher-approved safety method.

Official Cambridge syllabus