Question

F. Lithium floats an water while sodium
floats and catches fire when put in
water.​

Answer 1

Explanation:

Lithium's density is only about half that of water, so it floats on the surface, fizzing and giving off hydrogen gas. ... The reaction generates heat slowly, and lithium's melting point is too high for it to melt (this is not the case for sodium).

Answer 2

Sodium + Water = Reaction Exothermic

Explanation:

Lithium is one of the lightest elements - lighter than oxygen. It is about half as dense as water.

Sodium is also lighter than water .

∴ Both will float on water

But when sodium reacts with water the reaction is highly exothermic releasing a lot of heat that tends to catch fire in the water.

Thus, Lithium floats on water while sodium floats and catches fire when put in water.​