Read the descriptions below of two substances and an experiment on each. Decide whether the result of the experiment tells you the substance is a pure substance or a mixture, if you can.

Sample A is a solid yellow cube with a total mass of 50.0 g. The cube is put into a beaker filled with 250. mL of water. The cube collapses into a small pile of orange powder at the bottom of the beaker. When this powder is filtered out, dried and weighed, it has a total mass of 29.9 g. If the experiment is repeated with 500. mL of water, the powder that's left over has a mass of 10.0 g.

Sample B is 100. g of a coarse grey powder with a faint unpleasant smell. 15. g of the powder is put into a funnel lined with a sheet of thick paper. Distilled water is poured slowly over the powder. Most of the powder disappears, but of a gritty black sand-like material is left on the surface of the paper. Pouring more water over the black material doesn't change how much of it there is.

Is sample A made from a pure substance or a mixture?