Which one of the following is not a chemical change ?

A chemical change involves the formation of new substances through chemical reactions, whereas a physical change alters only physical properties without changing chemical composition [1]. Burning of coal is a combustion reaction that produces carbon dioxide, a new substance [4]. Fermentation of sugarcane juice is a biochemical process where sugars are converted into alcohol and carbon dioxide by yeast, representing a chemical change [t4][t5]. Cracking of petroleum involves breaking down complex long-chain hydrocarbons into smaller molecules, which is a chemical process [t2]. In contrast, the crystallisation of table salt from seawater is a physical change [t1]. It involves the evaporation of water, leaving behind salt crystals; the chemical identity of the sodium chloride remains unchanged throughout the process, and it can be reversed by redissolving the salt [t1][t3].

Sources

1. [1] Science-Class VII . NCERT(Revised ed 2025) > Chapter 5: Changes Around Us: Physical and Chemical > In a Nutshell > p. 68
2. [4] http://www.osha.gov/otm/section-4-safety-hazards/chapter-5