Question

read the description below of a substance and an experiment on it. decide whether the result of the experiment tells you the substance is a pure substance or a mixture, if you can.

• the sample 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 thats left over has a mass of 30.0 g.

is the sample made from a pure substance or a mixture?
if the description of the substance and the outcome of the experiment isnt enough to decide, choose \cant decide.\
pure substance
mixture
(cant decide)

Explanation:

A pure substance has a uniform composition and consistent properties throughout. A mixture consists of two or more substances physically combined. In this experiment, the powder is being tested with water. If it were a pure substance, it would either fully dissolve (if soluble) or not dissolve at all (if insoluble) in a consistent way. However, the fact that after filtering, drying and weighing, the mass of the powder recovered ($29.9$ g) is different from the initial mass ($30.0$ g) suggests that there might be some impurity or that it is a mixture. But this small mass difference could also be due to experimental error (e.g., some powder sticking to the filter paper). Since the evidence is not conclusive (could be experimental error or a mixture), we cannot be certain.

Answer:

(can’t decide)