Hey guys im gonna fail if i dont get these answer theses question right pls help me science is so hard

Which type of reaction always has an element and a compound as reactants

Ageochemist examines a piece of metal that he found in the soil. he performs tests to identify the metal from its density, electrical conductivity, and melting point. which statement best describes his investigation? a. he is determining physical properties that are sufficient to identify the metal. b. he is determining chemical properties that are sufficient to identify the metal. c. he is determining physical properties that are insufficient to identify the metal. d. he is determining chemical properties that are insufficient to identify the metal.

The lab procedure involves several factors, listed below some were variable and some were constant. label each factor below v for variable ot c for constant