Alkali metals are usually kept under

Alkali metals, particularly sodium and potassium, are extremely reactive elements. They react vigorously with oxygen and moisture present in the air, often catching fire spontaneously [2]. When they come into contact with water, the reaction is highly exothermic and produces hydrogen gas, which can ignite immediately [t2]. To prevent these hazardous reactions and protect the metals from oxidation, they must be stored in a medium that acts as a barrier to air and moisture. Kerosene (or mineral oil) is the standard storage medium because it is non-reactive with these metals and effectively seals them from the atmosphere [c1][t2][t8]. While other non-polar liquids like petrol could theoretically work, kerosene is preferred in laboratory and industrial settings due to its lower volatility and safety profile compared to petrol or absolute alcohol [t9].

Sources

1. [1] Science-Class VII . NCERT(Revised ed 2025) > Chapter 4: The World of Metals and Non-metals > Activity 4.6: Let us investigate (demonstration activity) > p. 52
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > Activity 3.9 > p. 42