CIE Chemistry AS Level
rate of reaction
a measure at rate in which the reactants are used up/ the rate at which the products are formed
reversible reaction
a reaction in which the products can change back into the reactants by reversing the conditions
catalyst
a substance that increases the rate of a reaction but remains chemically unchanged itself at the end of the reaction
standard condition
conditions of temperature and pressure that must be the same in order to compare moles of gases or enthalpy changes accurately.
relative atomic mass
mass of one atom of an element relative to 1/12 of the mass of an atom of carbon-12, which has a mass of 12.00 atomic mass units.
molecular mass
mass of one atom of one molecule of an element or a compound relative to 1/12 of the mass of an atom of carbon-12, which has a mass of 12.00 atomic mass units.
dynamic equilibrium
molecules of reactants are being converted to products in the same rate as products are being converted to reactants
bond energy
the energy needed to break 1 mole of a particular bond in 1 mole of gaseous molecules.
ionisation energy
the energy needed to remove 1 mole of electrons from 1 mole of atoms of an element in a gaseous state
enthalpy change of reaction
the energy transferred in a chemical reaction
molecular formula
the formula that tells us the actual numbers of each type of atom in a molecule
relative formula mass
the mass of one formula unit of a compound measured on a scale on which an atom of the carbon-12 isotope has a mass of exactly 12 units.
activation energy
the minimum energy that colliding particles must possess for a successful collision that results in a reaction to take place
empirical formula
the simplest formula of a compound; shows the ratio of the number of atoms of different elements in a compound
mole
the unit amount of substance
isotopic masses
when an element has the same number of protons but different number of neutron; hence different masses