Question

Which of the following changes cannot be reversed?

(a) Blowing a balloon

(b) Folding a paper to make a toy aeroplane

(c) Rolling a ball of dough to make roti

(d) Baking cake in an oven

(e) Drying a wet cloth

(f) Making biogas from cow dung

(g) Burning of a candle

Answer 1

Reversible changes:

• Any changes which can be reversed or are a temporary conversion.
• Physical changes are generally reversible.
• Examples of physical changes are Melting, freezing, boiling water, etc.

Irreversible changes:

• Irreversible changes are permanent changes.
• Chemical changes are generally irreversible changes.
• Examples of chemical changes are Cooking food and the Formation of water from Hydrogen as well as Oxygen.

The changes that cannot be reversed are:

• (c) Rolling a ball of dough to make roti
• (d) Baking cake in an oven
• (f) Making biogas from cow dung
• (g) Burning of a candle

The changes that can be reversed are:

• (a) Blowing a balloon
• (b) Folding a paper to make a toy aeroplane
• (e) Drying a wet cloth