For any pure substance, the boiling point and melting point will always remain

An unknown substance has a melting point of 1064 ∘c, is insoluble in water, conducts electricity as a solid, and is hard. given these properties, which of the following are possible identities for the unknown substance? check all that apply. view available hint(s) check all that apply. sio2 f2 au kbr

Idon’t quite understand this problem

Suppose an objects initial velocity is 10m/s and it’s final velocity is 4 m/s. mass is constant. what can best be concluded about the object based in the work-energy theorem