Question

Which of the following is not a desirable change?

• A. Formation of curd
• B. Formation of clouds
• C. Rusting of iron
• D. Ripening of fruits

Answer 1

The correct option is C

Rusting of iron

The explanation for the correct option:

Option C

• During the rusting of iron, the iron metal combines with oxygen in the air in the presence of water to form a hydrated iron oxide which is called rust.
• Due to rusting metals deteriorate gradually.
• So, it is an undesirable change.

Therefore, option C is correct.

The explanation for the incorrect option:

Option A

• The formation of curd is desirable as well as chemical change.
• Curd is made from milk, which is a new substance.

Therefore option A is incorrect.

Option B

• The formation of a cloud is a physical change.
• Cloud formation is a phase transformation cycle of natural water from liquid to gas and then gas to liquid.

Therefore option B is incorrect.

Option D

• Ripening of fruits is a chemical change.
• This change can not be reversed.
• Due to the ripening, the colour, texture, and taste of the fruits are changed.

Therefore option D is an incorrect option.