Industrial Preparation: the Contact Process The Contact process makes sulphuric acid in four stages: Forming sulphur dioxide — by burning […]

The Electronic Theory of Bonding Atoms combine in fixed ratios to form new substances, mainly through interactions between their valence […]

Sulphur Sulphur sits in Group VI, period 3, making up about 0.1% of the Earth’s crust, and occurs as free […]

What’s Inside an Atom An atom is the smallest particle of an element that can take part in a chemical […]

An element is a substance that cannot be broken down into simpler substances by chemical means. Elements are divided into […]

Acids Acids occur naturally in substances like unripe mangoes and oranges, giving them a sour taste. They have a sour […]

Key Terms Solution: a homogeneous (uniform) mixture of a solute and a solvent. Solvent: the majority component of a solution, […]

Hand picking: removing one component of a mixture by hand, e.g. picking stones out of rice. Sieving: separates solid particles […]

Water is often called the universal solvent because it can dissolve so many other substances. Hard and Soft Water Hard […]

Air is a mixture of gases: roughly 78% nitrogen, 21% oxygen, 0.03–0.04% carbon dioxide, plus variable amounts of water vapour, […]