International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

Which of the following describes a characteristic of a saturated hydrocarbon?

1. Contains at least one double bond

2. Contains only single bonds

3. Can form more bonds

4. Has a lower boiling point than unsaturated hydrocarbons

The correct answer is: Contains only single bonds

A saturated hydrocarbon is specifically defined as a hydrocarbon that contains only single bonds between carbon atoms. This means that all the carbon atoms in the saturated hydrocarbon are bonded to as many hydrogen atoms as possible, adhering to the formula CnH2n+2. The presence of only single bonds is significant because it distinguishes saturated hydrocarbons from unsaturated hydrocarbons, which contain at least one double or triple bond. This characteristic influences the reactivity and physical properties of the compound, making saturated hydrocarbons generally more stable and less reactive than their unsaturated counterparts. When considering the other options, a saturated hydrocarbon cannot contain double bonds, which directly supports the idea that it contains only single bonds. It also cannot form more bonds in the sense of adding additional hydrogen atoms, as it is already saturated. Additionally, saturated hydrocarbons typically have higher boiling points compared to their unsaturated analogs due to the stronger intermolecular forces (like van der Waals forces) that arise from their single-bonded structures. Thus, the defining feature of having only single bonds holds true and accurately describes saturated hydrocarbons.