Which one of the following is a physical change?

A physical change involves a change in physical properties without forming new substances, whereas a chemical change results in new molecular structures [4]. Burning coal and wood are combustion reactions that produce new substances like carbon dioxide and ash, making them chemical changes [4]. Heating potassium chlorate causes thermal decomposition into potassium chloride and oxygen, which is a chemical reaction [3]. In contrast, heating a platinum crucible is a physical change. Platinum is a noble metal with a very high melting point and excellent chemical stability; when heated in a laboratory setting, it simply increases in temperature or glows without reacting with atmospheric oxygen or changing its chemical composition. Since the platinum remains chemically identical before and after heating, it qualifies as a physical change [4].

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] https://education.nationalgeographic.org/resource/changes-matter-physical-vs-chemical-changes/
3. [2] Science-Class VII . NCERT(Revised ed 2025) > Chapter 5: Changes Around Us: Physical and Chemical > 5.3.2 Combustion > p. 62
4. [3] Science , class X (NCERT 2025 ed.) > Chapter 1: Chemical Reactions and Equations > Figure 1.4 > p. 8