So what unit do chemists use to count particles? Particles are so tiny, chemists use the unit of moles. A mole contains 6.02 x atoms. 602, 000, 000, 000, 000, 000, 000, 000

One mole of popcorn would cover every dry surface of the Earth to a depth of six miles One mole of stacked pennies would reach to the moon and back 16 times One mole of marshmallows would cover the US to a depth of 650 miles

1811- Avogadro- equal volumes of gases at the same temperature and pressure contained equal number of molecules Cannizzaro- developed atomic weights for known elements Loschmidt- determined the number of atoms present in given volume of air true value 6.02 x found

Recall the Law of Conservation of Mass Mass of reactants = mass of products Mass of starting substances = mass of ending substances 2 hydrogen atoms + 1 oxygen atom  1 water molecule

Law of Definite Proportions Regardless of amount, a compound will always be composed of the same elements in the same proportions by mass For example, two hydrogen atoms will always combine with one oxygen atom to produce one molecule of water

Moles ↔ Particles Conversion Particles Atoms, molecules x 6.02 x ÷ 6.02 x Moles

Convert 3.5 moles to atoms

Convert 18.06x10 23 atoms to moles

Convert from moles to particles 2.7 moles of lithium 1.8 moles of sodium chloride

Convert from moles to particles 5.3 moles of bromine 4.7 moles of potassium oxide

particles  moles 4.32 x atoms of calcium

particles  moles 2.7 x atoms of copper

particles  moles 2.5 x molecules of sodium chloride 5.32 x molecules of calcium chloride

You try these… 25 moles to particles 4.08 x 10 4 particles to moles moles to particles 2.3 x particles

Homework Complete on another sheet of paper showing your work! Moles to particles 2.7 moles 1.8 moles 5.3 moles 4.7 moles Particles to moles 4.32 X X X X 10 23