acidic solution
a solution in which there is a greater concentration of hydrogen ions (H+) than hydroxide ions (OH-)
activation energy
the minimum amount of energy required for a chemical reaction to occur
alkali metals
elements in group 1 of the periodic table
alkaline earth metals
elements in group 2 of the periodic table
alkaline solution
a solution in which there is a greater concentration of hydroxide ions (OH-) than hydrogen (H+) ions
allotrope
different forms of the same element
anhydrous
a substance that does not contain water
anion
a negatively charged ion
aqueous solutions
a solution with water as the solvent
atm
abbreviation for the atmosphere unit of pressure
atom
the smallest possible particle of an element
atomic number
the number of protons in an atom
Avogadro's hypothesis
equal volumes of all gases measured at the same temperature and pressure will contain the same number of particles (same number of moles)
catalyst
a substance that speeds up a chemical reaction but is not used up in the process
cation
a positively charged ion
coefficient
the number in front of a formula in a chemical equation
colligative property
a property that depends on the concentration of particles within the solution
compound
a substance that contains more than one element chemically combined
concentration
a measure of how much of a solute is dissolved in a given volume of solvent
conjugate acid
the substance formed when a base gains a proton (H+)
conjugate base
the substance formed when an acid loses a proton (H+)
coordinate covalent bond
a covalent bond formed when both electrons in the shared pair are provided by one atom
covalent bond
a link between two atoms comprising of a shared pair of electrons
crystallisation
the process by which a solid is formed from a solution
density
a measure of the mass for a given volume of a substance
dipole
a variation of electric charge from one place to another
discrete
particles that are separate from other particles
dissociation
the process of ions separating from each other
ductile
can be drawn into a wire
dynamic equilibrium
a system where there is no overall change due to the rate of the forward and reverse processes being equal
electrolysis
the splitting of a compound caused by passing an electric current though a molten substance or solution
electrolyte
a substance that can produce ions when dissolved in water
electronegativity
a measure of the relative ability of an atom to attract electrons
electrorefining
the process of using electrolysis to increase the purity of a substance
electrostatic forces
forces caused by the interaction of electric charges
electrowinning
the process of using electrolysis to extract metals from their ores
element
a substance that contains only one type of atom
empirical formula
the simplest whole number ratio of the atoms in a compound, written in the style of a formula
endothermic reaction
a reaction that absorbs heat energy from the surroundings
enthalpy
chemical potential energy
enthalpy change
the difference between the enthalpy of the products and the reactants
evaporation
the process of a liquid changing into a gas
excess
more than is required for a chemical reaction
exothermic reactions
a reaction that releases heat energy to the surroundings
formula unit
the group of atoms that is represented by the formula of the compound
group
vertical column in the periodic table
halogens
elements in group 17 of the periodic table
heterogeneous mixture
a mixture with composition and properties that are not the same throughout the mixture
homogeneous mixture
a mixture with uniform composition and properties throughout the mixture
hydrated
a substance that contains water
indicator
a chemical that changes colour dependent on the pH of the surrounding solution
intermolecular
between molecules
intramolecular
within a molecule
ion
a charged particle formed by the loss or gain of electrons from an atom or molecule
ionic equation
a chemical equation showing only the species that are changed in a chemical reaction
ionisation
the formation of an ion from an atom or molecule
ionisation energy
the energy required to remove an electron from the valence shell of an atom or ion
isotopes
atoms with the same atomic number but different mass numbers
kinetic energy
the movement energy of an object
limiting reagent
the substance that is used up first in a chemical reaction
macroscopic property
an observable characteristic of a substance
malleable
can be hammered into different shapes
mass number
the total number of protons and neutrons in an atom
mole
the quantity of a substance that contains Avogadro's number of particles
molecule
a particle comprised of more than one atom held together by covalent bonding
monatomic ion
an ion that contains one atom
networks
three-dimensional, regular arrangements where particles have fixed positions
neutral solution
a solution in which the concentrations of hydrogen ions (H+) and hydroxide ions (OH-) are equal
noble gases
elements in group 18 of the periodic table
octet
eight electrons on an electron shell within an atom
oxidising agent
a substance that causes another chemical to be oxidised in a chemical reaction
pH scale
a method of measuring acidity, the lower the pH value, the greater the acidity
period
horizontal row in the periodic table
polyatomic ion
ions that contain two or more atoms combined together
polyprotic acid
an acid that has the ability to donate more than one hydrogen ion per molecule
potential energy
stored energy
precipitation
the process by which a solid is formed by mixing two solutions
product
a substance made as a result of a chemical reaction
reactant
a substance used in a chemical reaction
reactivity
a measure of how vigorously an element will react with other substances
reagent
a substance involved in a chemical reaction
reducing agent
a substance that causes another chemical to be reduced in a chemical reaction
relative atomic mass
(Ar) the mass of an atom relative to the mass of a carbon-12 atom
relative molecular mass
(Mr) the mass of a molecule relative to the mass of a carbon-12 atom
salts
ionic substances that are produced by the neutralisation of an acid
saturated solutions
a solution where the maximum amount of solute has been dissolved in the solvent
sequestration
a method of storage of a chemical, normally used in relation to the storage of carbon-based compounds
solubility
a measure of how much of a substance is able to dissolve in a given volume of solvent
solute
a substance that dissolves into a solvent
solution
a homogeneous mixture with solute dissolved in a solvent
solvation
the process of a species dissolving in water
solvent
the substance that a solute dissolves into
species
a particle involved in a chemical process
spectator ions
ions that are not changed in a chemical reaction
standard temperature and pressure
(STP) a temperature of O °C and a pressure of 101.3 kPa
stoichiometric ratio
the ratio of the number of moles of substances involved in a chemical reaction
stoichiometry
calculations of quantities of substances involved in chemical reactions
sublimation
direct conversion between solid and gas
temperature
a measurement of the average kinetic energy of particles
transition elements
elements in groups 3-12 of the periodic table
valence shell
the outermost shell that contains electrons
valency
a measure of the combining power of a species
vapour pressure
the increase in pressure caused by particles evaporating from the surface of a liquid
volatility
a measure of how easy it is for a liquid to evaporate to form a vapour
VSEPR
valence shell electron pair repulsion
water of crystallisation
water that is contained within the structure of a solid crystal
yield
a measure of the amount of product from a reaction compared to the maximum amount possible from that reaction
