Question

Which among the following changes is irreversible in nature?

• A.
  Setting of cement
• B.
  Woollen yarn to knitted sweater
• C.
  Dissolution of sugar in water
• D.
  Melting of ice

Answer 1

The correct option is A

Setting of cement
Changes which cannot be reversed or undone are called irreversible changes.
The setting of cement is an example of irreversible change. Once the process of setting is complete, it cannot be returned to its original form.
We can obtain the sugar dissolved in water by the process of evaporation. Melted ice can be converted to its solid state upon cooling. Woollen yarn can be returned to its original form by unfastening the knots in the sweater.