Question

sodium and potassium are stored in kerosene

Answer 1

Metals such as potassium and sodium react with oxygen. when they are kept open the catch fire. To protect accidental fires they are kept immersed in Kerosene oil.

Hope this will help yoi

Answer 2

because they r very reactive and can react vigorously with oxygen of air and hence can catch fire.
hope it's helpful to you dear