Definitions and formulas

Temperature when a substance begins to change from solid to liquid

Temperature when a substance begins to change from liquid to gas

The force exerted by gas molecules colliding with surfaces of objects or other particles

The average kinetic energy of the particles in a substance

Diffusion is the net movement of particles from an area of high concentration to an area of low concentration until they’ve reached equilibrium.

Concentration is a measure of how much of a substance there is in a single area, in other words, the amount of substance per unit volume.

Pure substances made up of only one type of atom

Pure substances that are formed when two or more elements chemically combine

A combination of two or more substances (elements and/or compounds) that arenotchemically combined

Two elements bonded together

the number of protons in the nucleus of an atom

the total number of protons and neutrons in the nucleus of an atom

different atoms of the same element that have the same number of protons but different numbers of neutrons

Atomic mass= (fractional abundance of isotope 1 x mass number of isotope 1) + (fractional abundance of isotope 2 x mass number of isotope 2)

An ionic bond is a strong electrostatic attraction between oppositely charged ions

An ion is an electrically chargedatom or group of atoms formed by the lossor gain ofelectrons

A covalent bond is formed when a pair of electrons is shared between two atoms leading to noble gas electronic configurations

A simple molecular substance is a covalent substance that is made up of a small number of non-metal atoms held together with a small number of covalent bonds

A giant covalent structure is networks made up of a large number of non-metal atoms, held together with a large number of strong covalent bonds

An allotrope is two or more physical forms in which an element can exist. E.g. diamond and graphite are both made of carbon

the electrostatic attraction between the positive ions in a giant metallic lattice and a ‘sea’ of delocalised electrons

The number and type of different atoms in one molecule

The simplest whole number ratio of the different atoms or ions in a compound

The average mass of the isotopes of an element compared to 1/12th of the mass of an atom of 12^C