Norder to observe a property of a substance, the substance must interact with another substance, such as when gasoline burns or when sodium metal reacts with water.

Ido not understand. 

Use a magnet to separate iron, evaporate water, i'm not sure how to separate the other two i'm sorry but good luck

Answerδh > 0explanationc₆h₆  (s)  → c₆h₆ (l)if you are changing it from a solid to a liquid, you are pretty much melting the solid. this requires heat energy. therefore, the reaction is endothermic (takes in energy); the system enthalpy increases as the reaction proceeds: δh > 0.