HOW DO WE MAKE OUT WHETHER A REACTANT OR A PRODUCT IS A SOLID, LIQUID OR A GAS

Dear Student,

Just by looking at a reaction it is not possible to identify wheather a reactant is solid,liquid or gas.Usually the substance exists in more then one of these forms(solids,liquids or gaseous;for eg. CO₂exists as a solid below a certain temerature condition and as gas above that temperature condition).Hence we refer to the standard state of substance as per the given conditions(Temperature,pressure,solvents used etc.) for identifying the state the reactants/products.