Statement I: Conversion of blue copper sulphate to black cupric oxide on heating is a physical change. Statement II : A change in which chemical composition does not change is called physical change.

Statement I is false because the conversion of blue copper sulphate to black cupric oxide is a chemical change, not a physical one. When blue copper sulphate (CuSO4·5H2O) is heated, it first loses its water of crystallization to become white anhydrous copper sulphate [1]. Upon further strong heating, it undergoes thermal decomposition to form black copper(II) oxide (CuO) and sulfur trioxide gas [2]. This process involves a change in chemical composition and the formation of new substances, which defines a chemical change. Statement II is true as it provides the standard scientific definition of a physical change, where the substance's identity and chemical formula remain constant despite changes in state or appearance. Since Statement I is incorrect regarding the nature of the reaction, the correct option is 4.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 2: Acids, Bases and Salts > Activity 2.15 > p. 32
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 1: Chemical Reactions and Equations > Figure 1.4 > p. 8