Chemistry ATAR Chapters 1-8 (excluding nanotech)

alloy

alloy

A substance formed when other materials (e.g. carbon, other metals) are mixed with a metal.

centrifugation

A separation process that uses the action of rapid rotation to accelerate the settling of particles in a solid-liquid mixture.

ceramic

material that is produced by the firing (heating) of clay.

colloid

a mixture in which very small particles are spread throughout a liquid, solid or gas. these particles are bigger than single molecules but small enough that they do not settle on standing.

composite material

a combination of two or more distinct materials with significantly different physical and chemical properties.

compound

a pure substance made up of different types of atoms combined in a fixed ratio.

decantation

a separation process in which a later of liquid is separated from the solid that has settled at the bottom.

density

a measure of the amount of mass per unit volume.

distillation

the process of separating a solution by evaporating, condensing and collecting the component of the solution with the lowest boiling point.

element

a substance made up of atoms with the same atomic number.

filtrate

the purified liquid that collects in the flask when a mixture is filtered.

filtration

the process of removing solids from a liquid or gas by passing the mixture through a fine mesh or filter.

fractional distillation

a form of distillation that separated solutions of liquids according to their boiling point.

mineral

a naturally occurring inorganic substance that is solid and can be represented by a chemical formula, e.g. quartz

ore

a mineral or aggregate of minerals that contains a valuable constituent, such as a metal, which is mined or extracted

residue

the solid collected in the filter paper when a mixture is filtered

polymer

a long-chain molecule that is formed by the reaction of large numbers of repeating units (monomers)

sediment

the solid material that settles to the bottom of a body of water

sedimentation

the process of solid particles settling out of a liquid

separation funnel

a funnel with a large bulb and a tap in its output tube that is used to separate immiscible liquids

sieving

the process of separating large solid particles from smaller solid particles by passing the mixture through a mesh

suspension

a heterogenous mixture containing solid particles that are large enough to sink so the bottom of the mixture if it is left to stance (sedimentation), e.g. sand in a container of water that has just been shaken.

alpha particle

a positively charged particle formed by ionising radiation.

atomic number

the number of protons in the nucleus of an atom; identical to the charge number of the nucleus; symbol Z

atomic theory of matter

a theory proposed by John Dalton in 1802 that states that all matter is made up of atoms. he said that atoms are indivisible, atoms of the same element are identical and compounds are made up of different atoms in fixed ratios.

electrostatic attraction

the force of attraction between a positively charged particle and a negatively charged particle.

isotope

each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei.

mass spectrometer

an instrument that measures the mass-to-charge ratio of particles.

mass spectrum

a plot of the isotopic mass, relative to the mass of carbon-12 taken as 12 units exactly, against the relative abundance of each isotope present in a sample.

radioactive

spontaneously undergoing nuclear decay to produce radiation such as beta particles, alpha particles and gamma rays

relative atomic mass

the weighted average of the relative isotopic masses of an element on the scale where carbon-12 is taken as 12 units exactly

relative isotopic abundance

the percentage abundance of a particular isotope in a sample of an element.

relative isotopic mass

the mass of an atom of the isotope relative to the mass of an atom C-12 taken as 12 units exactly.

scanning tunnelling microscope (STM)

a microscope that images atoms by using a sharp metallic tip to sense the atoms on the surface of a crystal

standard atomic weight

the relative atomic mass of an element based on the agreed proportions of isotopes in a 'normal' sample of the element on earth

absorbance

a measure of the capacity of a substance to absorb light of a specified wavelength.

absorption line

the individual colours of light in a continuous spectrum that are absorbed by hydrogen atoms.

absorption spectrum

the collection of absorption lines.

atomic absorption spectroscopy (AAS)

an analytical technique that uses light absorption to measure the concentration of a metal in a sample.

atomic radius

a measurement used for the size of atoms; determined by measuring half the distance between two adjacent atoms in a molecule or structure.

bohr model

a theory of the atom proposed by Niels Bohr that states that electrons in an atom occupy fixed, circular orbits that correspond to specific energy levels.

core charge

the effective nuclear charge experienced by the outer-shell electrons in an atom. it indicated the attractive force felt by the valence electrons toward the nucleus.

electrical conductivity

the degree to which a specified material or solution conducts an electric current.

electromagnetic radiation

a form of energy that moved through space. visible light, radio waves and x-rays are forms of electromagnetic radiation.

electromagnetic spectrum

all possible frequencies of electromagnetic radiation shown in order of their wavelengths or frequencies.

electron shell

in the shell model of an atom, an electron shell is a fixed energy level that corresponds to a circular orbit of the electrons. in the Schrödinger model, a shell contains subshells and orbitals or equal or similar energy.

electronegativity

the ability of an atom to attract electrons in a covalent bond towards itself.

emission line

When an electron absorbs energy it jumps to a higher energy state. Shortly afterwards the electron returns to the lower energy level, releasing a fixed amount of energy as a particular colour of light.

emission spectrum

A spectrum produced when an element is excited by heat or radiation. It appears as distinct lines characteristic of the element.

excited state

A term used to describe an atom in which electrons occupy higher energy levels than the lowest possible energy levels.

first ionisation energy

the energy required to remove one electron from an atom of an element in the gas phase.

flame test

Determination of the metallic elements present in a compound by inserting a sample of the compound into a non-luminous Bunsen burner flame. Some metals produce particular colours when they are heated.

inert

not chemically reactive.

ionisation

the removal of one or more electrons from an atom or ion, or the reaction of a molecular substance with a solvent to form ions in solution.

ionisation energy

the energy required to remove one electron from an atom of an element in the gas phase.

metallic character

described how closely an element exhibits the properties commonly associated with metals, namely, that it readily loses an electron to form a cation. this is closely related to ionisation energy.

metalloid

an element that displays both metallic and non-metallic properties, e.g. germanium, silicon, arsenic, tellurium.

noble gas

an unreactive gaseous element in group 18 of the periodic table. with the exception of helium, noble gases have eight electrons in their outer shells.

octet rule

a rule used as part of the explanation for electron configuration and in bonding. the rule is that during a chemical reaction, atoms tend to lose, gain or share their valence electrons so that there are eight electrons in the outer shell.

quantised

in specific quantities or chunks.

spectroscopy

the study of the way that radiation, such as light and radio waves, interacts with matter.

successive ionisation energy

The energy required to achieve the sequential removal of electrons from the atom.

transition metal

an element in groups 3-12 in the periodic table

alkali metal

a group 1 metal - Li, Na, K, Rb, Cs and Fr

annealing

heating a metal to a moderate temperature and then allowing it to cool slowly to make it softer and more ductile

brittle

shatters when given a sharp tap.

conductivity

permitting the flow of electric charges.

conductor

an object or type of material that permits the flow of electric charges, e.g. a wire is an electrical conductor that can carry electricity along its length

crystal

a solid made up of atoms or molecules arranged in a repeating three-dimensional pattern.

delocalised electron

an electron that is not restricted to the region between two atoms.

ductile

able to be drawn into a wire

heat treatment

heating a metal in different ways to alter its structure and physical properties

interstitial alloy

an alloy made by adding smaller atoms to a metal.

lattice

a regular arrangement of large numbers of atoms, ions or molecules.

malleable

able to be bent or beaten into sheets.

metallic bonding

the electrostatic attractive forced between delocalised valence electrons and positively charged metal ions.

metallic nanomaterial

a material with metal atoms arranged to make structures that have at least one dimension that is 1-100nm

metallic lattice

tightly packed arrangement of metal atoms in a 'sea' of electrons.

molten

materials that are normally found as solids but are liquid, melted, due to elevated temperature.

quenching

heating a metal to a moderate temperature and then cooling it rapidly to make it harder and more brittle

reactivity

the ease with which a chemical can undergo reactions

reactivity series of metals

a ranking of metals in increasing order of their reactivity (ability to be oxidised) with the half-equations written as reduction equations of the corresponding ion. least reactive metals are at the top and most reactive metals are at the bottom.

steel

a generally hard, strong, durable and not malleable alloy of iron and carbon, usually containing 0.2-1.5% carbon, often with other constituents such as manganese, chromium, nickel, molybdenum, copper, tungsten, cobalt or silicon, depending on the desired alloy properties.

substitutional alloy

an allow made from elements of similar chemical properties and size

tempering

a process in which a metal that has been quenched is warmed again to a lower temperature to reduce its brittleness but to retain its hardness

tensile strength

the maximum resistance of a material to a force that is pulling it apart before breaking, measured as the maximum stress the material can withstand before tearing

work hardening

the increase in strength that results from processes such as hammering, rolling and drawing a metal

crystal lattice

the symmetrical three-dimensional arrangement of atoms or ions inside a crystal.

electrolyte

a solution or molten substance that conducts electricity by means of the movement of ions, e.g. a solution of sodium chloride

empirical formula

a formula that shows the simplest whole number ratio of the elements in a compound, e.g. CH2 instead of C3H6

ionic bonding

a type of chemical bonding that involves the electrostatic attraction between oppositely charged ions

ionic compound

a type of chemical compounds that involves electrostatic attraction between oppositely charged ions

polyatomic ion

an ion that is made up of more than one element

valency

the charge of an ion is equal to its valency. it is a measure of the combining ability of an atom with other atoms

ball-and-stick model

a model that displays both the three-dimensional position of the atoms and the bonds between them. the atoms are represented by coloured spheres that are connected by rods to represent the bonds.

covalent bond

the force of attraction formed when one or more pairs of electrons are shared between two nuclei.

diatomic molecule

a molecule formed from two atoms only.

double covalent bond

a covalent bond in which four electrons (two electron pairs) are shared.

intermolecular force

an electrostatic force of attraction between molecules, including dipole-dipole forces, hydrogen bonds and dispersion forces

intramolecular bond

a force that hols the atoms within a molecule together