A list of various changes is given. I. Burning of wood II. Melting of wax III. Dissolving sugar in water IV. Sawing of a piece of wood V. Ripening of fruits VI. Boiling of water In the given list, the irreversible changes are

Dear student. A change is called irreversible if it cannot be changed back again. In an irreversible change, new materials are always formed. Sometimes these new materials are useful to us. Example burning of paper is irreversible change because after burning of paper ash is formed this ash is not converted back to paper. So using the above definition we can identify that (I) burning of wood is an irreversible change because on burning wood turns into ash and smoke. (II) Melting of wax is a reversible change because molten wax can be solidified back. (III)Dissolving sugar in water is a reversible process because water and sugar can separated by the processes of crystallisation and condensation. (IV) Sawing of a piece of wood is an irreversible change because we cannot obtain the same piece of wood after sawing. (V) Ripening of fruit is an irreversible change. (VI) Boiling of water is a reversible change. Regards