How many hydrogen atoms are present in butene (C4H8) compared to butane (C4H10)? Explain the significance of this difference.

Butene (C4H8) has two fewer hydrogen atoms than butane (C4H10), which is significant because it indicates that butene is an unsaturated hydrocarbon. This unsaturation allows butene to participate in addition reactions that butane cannot.

This question assesses the student's ability to compare the molecular formulas of an alkene and an alkane, reinforcing the concept of unsaturation in alkenes. A strong answer highlights the implications of this difference in terms of chemical reactivity. This response is aligned to Structure and formulae of alkenes because it explains explain that alkenes are unsaturated because they contain two fewer hydrogen atoms than the alkane with the same number of carbon atoms using the correct AQA GCSE Chemistry organic context. Keep molecular formula, structural formula, displayed formula, and general formula distinct. Do not confuse alkanes with alkenes, saturated with unsaturated, cracking with combustion, polymers with monomers, or hydrocarbons with oxygen-containing alcohols and carboxylic acids. When formulae are used, preserve the stored notation exactly and explain the GCSE chemistry idea in words rather than using unsupported displayed-formula diagrams.