Water is a compound of hydrogen and oxygen, and life as we know it depends on it. Pure water is […]

Sources of Energy Heating something requires an energy source. The main ones are: Source Notes Renewable? Biomass Organic material — […]

Where Oxygen Comes From Oxygen sits in Group VI, period 2. It makes up 21% of atmospheric air by volume […]

Carbon Carbon is a Group IV, period 2 element — chemical symbol C, atomic number 6, electronic configuration 2,4. Allotropes […]

Group VII: An Overview The halogens — fluorine, chlorine, bromine and iodine — make up Group VII, each with seven […]

The pH Scale Acidity and basicity are measured on the pH scale, running from 0 to 14. Substances closer to […]

Reversible vs. Irreversible Most everyday chemical changes are irreversible — cooking, or neutralising hydrochloric acid with sodium hydroxide (HCl(aq) + […]

What a Salt Is A salt is the ionic compound formed when the replaceable hydrogen ion(s) of an acid are […]

Phosphorus: An Overview Phosphorus is in Group V, period 3, with atomic number 15. It exists in several allotropic forms, […]

What’s in Air Air is a colourless, odourless, tasteless mixture of gases surrounding the Earth — about 78% nitrogen, 21% […]