How much stuff is in a specified volume of a substance scientists use?

What is chemical symbol for hydrogen sulphide? Is cheese homogeneous or heterogeneous mixture? Is the same gas produced in different chemical reactions? Is ferex 150 stronger than a ferrous 325? How many moles of Hydrogen are in 2 moles of H2O? Many of all of the same type of atom? Which element has 3 electrons in the 2p sublevel? What type of bond between flouride and nitrogen? Will we run out of glass in the future? What means outer energy level? Why add of little amount from acetic anhydride in synthesis of acetanilide? What two elements Bunsen burner discovered? According to Einstein's equation if 1 kg of mass disappears during a reaction then .? Why is a filter paper is a poor material to powder a solid before introducing it into a melting tube? What type of bond in Solid xenon? How do you describe hydrogen? What function does Atp serve in Cells? Where to get epsom salt from? What is salt bath furnace? What elements have symbols that are the same as the element?

How much stuff is in a specified volume of a substance scientists use?