A physical change is one in which a substance undergoes a change in its physical properties like shape, size, or state, but no new substance is formed. Statement (i) is correct because the state may or may not change during a physical change (e.g., melting ice changes state, but crushing chalk only changes shape). Statement (iii) is correct because the defining characteristic of a physical change is that no new substance is formed. Statements (ii) and (iv) describe chemical changes where new substances with different properties are formed through chemical reactions.