THE MOLE Unit 7

One way to measure how much substance available is to count the # of particles in that sample –However, atoms & molecules are extremely small –Also, the # of individual particles in even a small sample is very large –Therefore, counting the # of particles is not a practical measure of amount To solve this problem, scientists developed the concept of the mole –It’s the “chemical counting unit” One way to measure how much substance available is to count the # of particles in that sample –However, atoms & molecules are extremely small –Also, the # of individual particles in even a small sample is very large –Therefore, counting the # of particles is not a practical measure of amount To solve this problem, scientists developed the concept of the mole –It’s the “chemical counting unit” How Scientists Keep Track of Atoms

Just as a dozen eggs equals 12 eggs, a mole = 602,000,000,000,000,000,000,000 –It is equal to that number no matter what kind of particles you’re talking about –It could be represent marbles, pencils, or bikes –usually deals with atoms and molecules The word “mole” was introduced about 1896 by Wilhelm Oswald, who derived the term from the latin word moles meaning a “heap” or “pile.” The mole, whose abbreviation is “mol”, is the SI base unit for measuring amount of a pure substance. Just as a dozen eggs equals 12 eggs, a mole = 602,000,000,000,000,000,000,000 –It is equal to that number no matter what kind of particles you’re talking about –It could be represent marbles, pencils, or bikes –usually deals with atoms and molecules The word “mole” was introduced about 1896 by Wilhelm Oswald, who derived the term from the latin word moles meaning a “heap” or “pile.” The mole, whose abbreviation is “mol”, is the SI base unit for measuring amount of a pure substance.

The mole, as a unit, is only used to count very small items –Represents a # of items, so, we can know exactly how many items are in 1 mole The experimentally determined number a mole is called, Avogadro’s Number. –Or 6.02x10 23 The term representative particle refers to the species present in a substance –Usually atoms –Molecules –Or formula units (ions) The mole, as a unit, is only used to count very small items –Represents a # of items, so, we can know exactly how many items are in 1 mole The experimentally determined number a mole is called, Avogadro’s Number. –Or 6.02x10 23 The term representative particle refers to the species present in a substance –Usually atoms –Molecules –Or formula units (ions)

REPRESENTATIVE PARTICLES & MOLES ATOMIC NITROGEN ATOMN 6.02x10 23 NITROGEN GAS MOLEC. N2N2N2N2 6.02x10 23 WATERMOLEC. H20H20H20H20 CALCIUM ION ION Ca x10 23 CALCIUM FLUORIDE FORMULA UNIT CaF x10 23

How Do We Use The Mole? We’d never use the mole to describe macroscopic or real world objects. –1 mole (6.02x10 23 ) of watermelon seeds would be found inside a watermelon the size of the moon. –1 mole (6.02x10 23 ) of donut holes would cover the earth and would be 5 miles deep. Since the mole is such a huge number of items, it is only used to describe the amount of things that are very, very small. –1 mole (6.02x10 23 ) of water molecules would barely fill a shot glass We’d never use the mole to describe macroscopic or real world objects. –1 mole (6.02x10 23 ) of watermelon seeds would be found inside a watermelon the size of the moon. –1 mole (6.02x10 23 ) of donut holes would cover the earth and would be 5 miles deep. Since the mole is such a huge number of items, it is only used to describe the amount of things that are very, very small. –1 mole (6.02x10 23 ) of water molecules would barely fill a shot glass