The correct option is 3.
In the presence of oxygen, iron will react with water to form rust. This is a chemical reaction and it is one of the chemical properties of iron.
Chemical properties refers to those properties of a substance, which can be used to identify it chemically, that is by reason of chemical reactions. Examples of chemical properties are reactivity with water, heat of combustion, electromotive force, pH, etc.<span />
The third one because
Most minerals can be characterized and classified by their unique physical properties: hardness, luster, color, streak, specific gravity, cleavage, fracture, and tenacity.
Na5Cl2
penta is 5, so 5 sodiums and di is 2, so 2 chloride
6.8x10^4
Would be the answer in scientific notation
