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 candle wax

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, its chemical properties are altered and it cannot be returned to its original form.

We can obtain the sugar dissolved in a solution by the process of evaporation. Melted wax 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.