Describe two test that you can run to determine if something is a substance or a mixture

To determine if something is a substance or a mixture you can centrifuge it and/or look at its warming curve.

Explanation:

Centrifugation is a method of separating heterogeneous mixtures of solids with liquids or only liquids. One of the most important factors in centrifugation is density. This is because centrifugation separates what is denser from what is less dense. What is denser is at a lower level, while the less dense rises. Thus, centrifugation can be used as a test if something is a substance or a mixture. This is because if, after going through the centrifugation process, this "something" has two phases it means that it is a mixture; presenting a single phase is a substance.

Another very useful test in chemistry to identify if something is a substance or a mixture is the so-called warming curve. A solid-state sample is taken at a temperature and subjected to constant heating. The solid sample warms up until it begins to melt. Transformed into liquid continues to heat until boiling. Even after being turned into gas, it can still be heated.

If the boiling point and melting point have a constant temperature we can say that the sample is a pure substance. If one or both of them vary, it is a mixture.