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