When water is changed into ice, its volume increases by 10%. If ice is changed into water, the percentage decrease in its volume will be:

Correct option is C

Given:

Volume increase when water turns into ice = 10%

Concept Used:

Volume change upon phase transition: The volume change percentage is reversed when the substance is converted back to its original state.

Formula Used:

Volume change on reversing a process = $$\text{Initial Volume} \times \left( 1 + \frac{\text{percentage change}}{100} \right)$$​​

Solution:
When water changes into ice, the volume increases by 10%, meaning the ice occupies 110% of the volume of the water.

Now, if the ice is changed back into water, the volume will decrease, and the volume of water will be 100% of the original volume.

The percentage decrease in volume is:

Percentage decrease = $$\frac{\text{Volume of ice} - \text{Volume of water}}{\text{Volume of ice}} \times 100$$​​

Since the volume of ice is 110% of the volume of water:

Percentage decrease = $$\frac{110\% - 100\%}{110\%} \times 100 = \frac{100}{11} \%$$​​