Which one among the following is not a chemical change?

A physical change involves a change in physical properties without forming new substances, whereas a chemical change results in the formation of one or more new substances [2]. Evaporation of water is a physical change because it involves a change in the state of matter (liquid to gas) without altering the chemical identity of the water molecules [2]. In contrast, curdling of milk is a chemical change as it involves the formation of new substances like lactic acid. Ripening of fruit is a biochemical process that changes the chemical nature of the fruit [3]. Burning of coal is a combustion reaction, which is a classic chemical change where coal reacts with oxygen to produce new substances like carbon dioxide and heat [2]. Therefore, evaporation is the only physical change among the options.

Sources

1. [1] Science-Class VII . NCERT(Revised ed 2025) > Chapter 5: Changes Around Us: Physical and Chemical > In a Nutshell > p. 68
2. [2] https://sathee.iitk.ac.in/article/chemistry/chemical-and-physical-change-examples/
3. [3] Science-Class VII . NCERT(Revised ed 2025) > Chapter 5: Changes Around Us: Physical and Chemical > 5.6 Are All Changes Desirable? > p. 66