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 1023 atoms.

602, 000, 000, 000, 000, 000, 000, 000

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

• 1861- Cannizzaro- developed atomic weights for known elements

• 1865- Loschmidt- determined the number of atoms present in given volume of air

• 1971- true value 6.02 x 1023 found

Recall the Law of Conservation of Mass

Mass of reactants = mass of productsMass 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

ParticlesAtoms, molecules

x 6.02 x 1023

÷ 6.02 x 1023

Moles

Convert 3.5 moles to atoms

Convert 18.06x1023 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 1024 atoms of calcium

particles moles

• 2.7 x 1020 atoms of copper

particles moles

• 2.5 x 1024 molecules of sodium chloride

• 5.32 x 1023 molecules of calcium chloride

You try these…

• 25 moles to particles

• 4.08 x 104 particles to moles

• 0.002 moles to particles

• 2.3 x 1016 particles

HomeworkComplete 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 1024

2.70 X 1020

2.50 X 1024

5.32 X 1023