What evidence is there (i) that sodium has a low melting point; that (ii) sodium is malleable and ductile?
You really are making us squint...........
What evidence is there that sodium has a low melting point? There is EXPERIMENTAL evidence of same: sodium metal has a melting point of
And that sodium is soft? Again, there is experimental evidence evidence of same.
You can cut sodium with a blunt knife. You can compress it with your fingers. Some labs have a sodium press, where a block of sodium is pushed thru a small hole in a metal die so that a long, thin, ribbon of sodium wire emerges into a solvent (the which you want to dry efficiently).
Ask your chemistry teacher to give you a bit of sodium metal, and place the metal in a plastic bag with a bit of oil (under which the sodium is stored). Take a rolling pin (or a bit of metal tube of the the same dimensions), and you will find that the sodium is so malleable that you can roll it out as you would pastry, I kid you not.
And evidence that a gas is produced when you place the sodium in a protic solvent:
Place a small portion of sodium in ethanol (in water it will go bang!). The sodium metal will quite vigorously effervesce. You still have to establish the identity of the liberated gas. How to do that?