State two reasons for supposing that brass is a mixture and not a compound.

Sure, here are two reasons:

Variable Composition: Brass is an alloy made by mixing copper and zinc. The proportions of copper and zinc in brass can vary widely, depending on the desired properties such as hardness, color, and corrosion resistance. This variability in composition suggests that brass is a mixture rather than a compound, as compounds have fixed ratios of elements.
Physical Properties: Brass exhibits physical properties that are intermediate between those of its constituent elements, copper and zinc. For example, brass is typically harder and has a lower melting point than copper, but it's not as brittle as zinc. These properties are characteristic of mixtures where the properties of the components are retained to some extent, rather than being completely altered as in compounds.