Question

In which one of the following situations a chemical reaction does not occur?

• A. Milk is left open at room temperature during summer
• B. Grapes get fermented
• C. An iron nail is left exposed to humid atmosphere
• D. Melting of glaciers

Hint:

A physical change involves a change in state or appearance without changing the chemical identity, such as the melting of glaciers.

Answer 1

The Correct Option is D

In option (1), when milk is left open at room temperature, bacteria in the air may lead to fermentation, a chemical process.
In option (2), grapes undergo fermentation, which is a metabolic chemical reaction.
In option (3), when an iron nail is exposed to a humid atmosphere, it reacts with water and oxygen to form rust (iron oxide), a chemical reaction.
In option (4), the melting of glaciers is a physical change, not a chemical reaction, as there is no new substance formed. 
Thus, the correct answer is option (4).