(a) Name the prop

(a) A pure substance has a fixed melting point or boiling point at constant pressure. The purity of a substance can be tested by checking its melting point or boiling point. If a substance is impure i.e. it contains traces of another substance, the melting and boiling point of that substance will change.

(b) Alloys are homogeneous mixtures of metals and cannot be separated into their components by physical methods. But still, an alloy is considered as a mixture because it shows the properties of its constituents and can have variable composition.