Question

The change of a bud into a flower is a change that cannot be reversed. Give four more such examples.

Answer 1

The change of a bud into a flower is a change that cannot be reversed because this is an irreversible change.

Physical or chemical changes are categorized based on some of the criteria and reversibility is one of the important criteria.

Reversibility: The changes either physical or chemical can be of two types which are reversible or irreversible.

• Reversible change: The change which can be reversed in its initial stage whether it is a physical or a chemical change is called reversible change. Most of the time physical changes are reversible.
• For example, Melted Ice(liquid) can be again frozen into a cube of ice (solid) which is a physical change.
• In Haber's process, the ammonia which is formed by the reaction of nitrogen and hydrogen can be converted to nitrogen and hydrogen again.

$$\begin{gathered} \mathrm{Haber}\text{'}\mathrm{s}\mathrm{process}: \\ {\mathrm{N}}_2+3{\mathrm{H}}_2\stackrel{\mathrm{Fe}}{\rightleftharpoons }2{\mathrm{NH}}_3 \end{gathered}$$

• Irreversible change: The changes that can not be reversed back to their initial state are called irreversible change. Most of the chemical changes are irreversible.

Examples of changes that cannot be reversed are listed below.

• Digestion of food
• Ripening of fruits
• Burning of wood
• Milk into curd