 One example is the word “gross”. If you have a gross of something, you have 12 dozen or 144 items.  Can you think of any other words that are used to represent specific numbers?

 Chemists must work with large groups of atoms due to their small size just as bakers work with groups of 12.  Chemists called their group a mole (just as bakers call their group a dozen).  How many objects make up a mole?  A mole = 602,000,000,000,000,000,000,000 or 6.02 x 10 23

 A mole of paperclips hooked together in a chain would circle the earth 50 trillion times.  A mole of marshmallows would make a 12 mile thick layer covering the entire face of the earth.  A mole of popcorn kernels could cover the USA and be 5 miles deep.  If you could spend 1 billion dollars a second, it would take you 19 million years to spend a mole of dollar bills.  If you could count atoms at a rate of 1 million a second, it would take 20 billion years to count a mole of them.

 Count the number of beans in your bag. Compare with the person sitting next to you.  What do your samples have in common?  What is different about your samples?  How many dozen beans are in your bag?  Observe the samples of zinc, aluminum, copper, carbon, and sulfur.  What do the samples have in common?  What is different about the samples?  How is the volume different if the number of particles in each is the same?

10 1. pair 2. dozen 3. mole 4. ream

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 What is the mass of 1 carbon atom?  12 amu (12 atomic mass units)  The atomic mass scale is a relative scale based on the carbon atom.  The masses of all other atoms are based on how their masses compare to carbon’s.  For example, magnesium is twice as heavy as a carbon atom. What is its mass?  24 amu  Hydrogen was discovered to be 1/12 the mass of carbon, so its mass is 1 amu.  A chlorine atom is approximately 3 times as heavy as a carbon atom so its mass is approximately 36 amu.

 In the lab, scientists measure the amount of matter in terms of grams.  Therefore, chemists wanted to know how many atoms of carbon would be needed to have a mass of 12 g.  A professor by the name of Amadeo Avogadro determined this number to be 6.02 x  This number is now referred to as Avogadro’s number.

 1 mole of carbon = 6.02 x atoms of carbon = 12 grams of carbon  1 mole of hydrogen = 6.02 x atoms of hydrogen= 1 gram of hydrogen  1 mole of aluminum = 6.02 x atoms = 27 grams

 2 moles of carbon = x atoms of carbon = 24 grams of carbon  ½ a mole of carbon = 3.01 x atoms of carbon= 6 grams of carbon  3 moles of carbon = x atoms = 36 grams  1.5 moles of carbon = 9.03 x atoms = 18 grams

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 1 dozen of water molecules is how many?  12  How many molecules are in 1 mole of water (H 2 0)?  6.02 x  What is the mass of 1 molecule of water?  18 amu  What is the mass of 1 mole of water?  18 grams  How many molecules are in 2 moles of water?  x  What is the mass of 2 moles of water?  36 grams

amu grams amu grams

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