Reactions

Acids react with metal carbonates to produce a salt, water, and carbon dioxide gas; the CO₂ turns limewater milky.

In a chemical reaction the atoms of the reactants are rearranged into new combinations to form the products; no atoms are created or destroyed.

Carbon monoxide is a colourless, odourless, toxic gas; it binds to haemoglobin in red blood cells more strongly than oxygen, preventing oxygen transport.

A more reactive metal displaces a less reactive metal from a solution of its salt; e.g. iron added to copper sulfate solution displaces copper.

Carbon acts as a reducing agent when used to extract metals from metal oxides; carbon is oxidised to carbon dioxide while the metal oxide is reduced to the metal.

Acids react with metals (above hydrogen in the reactivity series) to produce a salt and hydrogen gas; the hydrogen gas 'squeaky pop' test confirms its presence.

Breaking chemical bonds takes in energy (endothermic) while making new bonds releases energy (exothermic); the overall energy change decides whether a reaction is exothermic or endothermic.

Combustion is an exothermic reaction between a fuel and oxygen that releases thermal energy and light.

Galvanising is coating iron with zinc to protect it from rusting; zinc is more reactive than iron and reacts with oxygen and water first (sacrificial protection).

Combustion is an oxidation reaction — the fuel gains oxygen; the word equation for burning carbon: carbon + oxygen → carbon dioxide.