Choose the color corresponding to each class of matter and use it to mark the formulas of the substances that belong to that class in the list. Note that some substances on the list do not belong to any class.
First, pick the color corresponding to the class of matter, then click on the correct formula.
HCl, CO2, NaCl, Al(OH)3, Fe2O3, CaCO3, MgO, H2, KOH, N2O5, H3PO4, HBr, FeCl3, CuSO4, NaI, Mg(OH)2, O2, H2S