Statement I : Conversion of coal to diamond is a physical change. Statement I : Physical change does not change the composition of the material.

Statement I is false because the conversion of coal to diamond is a chemical change, not a physical one. While both are carbon-based, coal is an impure form of carbon containing elements like oxygen and hydrogen, whereas diamond is a pure crystalline allotrope [t6]. The transformation involves a fundamental change in chemical structure and bonding—from the amorphous, impure state of coal to the rigid, three-dimensional covalent network of diamond [c1, t4]. Statement II is true as a general definition: a physical change involves changes in physical properties (like state or shape) without altering the substance's chemical composition [c3, t1]. However, since the conversion of coal to diamond involves breaking and forming new chemical bonds and changing the purity/identity of the substance, it constitutes a chemical change [c4, t1]. Thus, Statement I is false and Statement II is true.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 4: Carbon and its Compounds > Allotropes of carbon > p. 61
2. [2] Science-Class VII . NCERT(Revised ed 2025) > Chapter 5: Changes Around Us: Physical and Chemical > In a Nutshell > p. 68
3. [3] Science-Class VII . NCERT(Revised ed 2025) > Chapter 5: Changes Around Us: Physical and Chemical > Activity 5.4: Let us experiment > p. 61