CHEMISTRY KEYWORDS:
Kinetic theory: The theory that particles in gases
and liquids are in constant movement. The kinetic theory can be used to explain
the effect of temperature and pressure on the volume of a gas as well as rates
of chemical reactions.
Real gas: Gas that does not obey the ideal gas law, especially
at low temperatures and high pressures.
Vaporisation: State change when a liquid changes
to vapour.
Condensation: State change when a vapour changes
to a liquid.
Vapour pressure: Pressure exerted by a vapour in
equilibrium with a liquid.
Lattice: Regularly repeating arrangement of ions,
atoms or molecules in 3 dimensions.
Crystal lattice: Regular structure of crystals due to
the regular packing of the particles within the crystal.
Alloy: Mixture of 2 or more metals or a metal with a
non-metal.
Giant molecular structure / giant covalent structure:
Structure having a 3-dimensional network of covalent bonds throughout the whole
structure.
Allotrope: Different crystalline or molecular forms
of the same element. Graphite and diamond are allotropes of carbon.
Buckminsterfullerene: Simple molecular structure of
carbon, with formula C60. The molecule has the shape of a football
(soccer ball). The carbon atoms are arranged a the corners of 20 hexagons and
12 pentagons. The bonds where 2 hexagons join are shorter than those between
the hexagons and the pentagons.
Nanotube: Fullerene of hexagonally arranged carbon
atoms like a single layer of graphite bent into the form of a cylinder.
CHEMISTRY DEFINITIONS:
Ideal gas: Gas whose volume varies in proportion to
the temperature and inverse to the pressure. Noble gases such as
helium and neon approach ideal behaviour because of their low intermolecular
forces.
SUMMARY:
Ideal gases have zero particle volume and no intermolecular
forces of attraction.
The ideal gas equation pV = nRT can be used to calculate the volume of a gas under different conditions of temperature and pressure.
The ideal gas equation can be used to determine the relative
molecular mass of simple molecules.
Ionic compounds form a giant three-dimensional lattice
structure containing ions in a regularly repeating pattern. The high melting
points of ionic substances are due to strong ionic forces acting in all
directions between the ions.
The low melting points of simple molecular structures such
as iodine are due to weak intermolecular forces between the molecules.
The high melting points of giant molecular structures such
as diamonds are due to the large number of strong covalent bonds arranged in a
regularly repeating pattern.
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