Changes of State are Physical

A change of state involves matter transitioning between solid, liquid, or gaseous forms (e.g., melting, freezing, boiling, condensation). These transformations alter the physical arrangement and energy of the molecules but not their fundamental chemical identity. Therefore, a change of state is classified as a physical change because the substance remains chemically the same before and after the transition. For instance, when ice (solid water) melts into liquid water, it is still H₂O.

Statement A, "A change of state of matter is a physical change," is correct.

Irreversibility of State Changes

Statement B claims that a change of state is an irreversible change. This is generally incorrect. Most changes of state are readily reversible under different conditions. For example, water can freeze into ice (liquid to solid) and then melt back into water (solid to liquid) by simply adjusting the temperature. Similarly, water can boil into steam (liquid to gas) and condense back into water (gas to liquid).

Since changes of state are typically reversible, Statement B is incorrect.

Conclusion on Correct Statements

Based on the analysis:

• Statement A is correct (changes of state are physical changes).
• Statement B is incorrect (changes of state are typically reversible, not irreversible).

Therefore, only Statement A is correct.