Year 11 Chemistry Topic 2: Properties and Structure of Materials

Vocabulary flashcards covering pure substances, separation techniques, bonding structures, intermolecular forces, carbon allotropes, hydrocarbons, and nanomaterials.

Element

A pure substance made of only one type of atom (e.g. copper wire).

Compound

A pure substance made of two or more elements chemically bonded together in fixed proportions (e.g. distilled water, $H_2O$).

Homogeneous mixture

A mixture with a uniform composition throughout such that the different parts cannot be distinguished (e.g. air, brass).

Heterogeneous mixture

A mixture with a non-uniform composition containing visible phases or parts (e.g. soil, granite, muddy water, oil and water).

Filtration

A separation technique best suited for separating an insoluble solid from a liquid (e.g. sand from water).

Evaporation / crystallisation

A separation technique best suited for separating a dissolved solid from a solution (e.g. salt from salt water).

Simple distillation

A separation technique best suited for separating a solvent from a solution (e.g. water from salt water).

Fractional distillation

A separation technique best suited for separating two or more liquids with different boiling points (e.g. ethanol and water).

Magnetism

A separation technique best suited for separating a magnetic solid from a mixture of solids (e.g. iron filings from sand).

Chromatography

A separation technique best suited for separating substances with different solubilities or polarities (e.g. dyes).

Decanting

A separation technique best suited for a rough separation of a liquid from a settled solid.

Ionic lattice

A structure of positive and negative ions held by strong electrostatic attraction in a repeating 3D lattice, characterized by high melting points, brittleness, and conductivity only when molten or dissolved.

Metallic lattice

A structure of positive metal ions in a lattice surrounded by a sea of delocalised electrons, characterized by high melting points, malleability, ductility, and electrical conductivity in both solid and liquid states.

Molecular covalent

A structure composed of small, discrete molecules with strong covalent bonds within molecules and weak intermolecular forces between them, resulting in low melting/boiling points and non-conductivity.

Giant covalent network

A structure where atoms are covalently bonded into one continuous network, exhibiting very high melting points and non-conductivity (with exceptions such as graphite).

Intramolecular bonds

Strong covalent bonds within a molecule that are not broken when a molecular substance melts or boils.

Intermolecular forces

Weaker forces of attraction between separate molecules that are overcome during melting or boiling.

Dispersion forces (London forces)

Temporary, weak attractions present in all molecules caused by random, fleeting uneven electron distribution.

Dipole-dipole forces

Intermolecular attractions occurring between the permanent positive end of one polar molecule and the permanent negative end of another.

Hydrogen bonding

A special, stronger dipole-dipole force occurring when hydrogen is bonded directly to a small, highly electronegative atom ($N$, $O$, or $F$).

Diamond

A carbon allotrope where each C is bonded to 4 others in a rigid 3D tetrahedral network, making it extremely hard, non-conductive, and ideal for cutting tools and drill tips.

Graphite

A carbon allotrope where each C is bonded to 3 others in flat hexagonal layers held by weak dispersion forces, making it soft, conductive along layers, and useful as pencil lead, electrodes, or lubricant.

Graphene

A carbon allotrope consisting of a single, one-atom-thick layer of graphite that is very strong, flexible, and an excellent electrical conductor.

Alkanes

Saturated hydrocarbons containing only single C–C bonds with general formula CH₂₂ that are relatively unreactive and do not decolourise bromine water in the dark.

Alkenes

Unsaturated hydrocarbons containing at least one C=C double bond with general formula CH₂ that rapidly decolourise orange/brown bromine water.

Nanomaterials

Materials having at least one dimension in the range $1\text{--}100\text{ nm}$, providing a high surface-area-to-volume ratio that significantly alters their properties.