Pair Gross Ream 12 2 144 500 Counting MampMs Example 1How many MampMs are in one partysized bag Given on the bag 1 bag 11907g We want MampMs per bag ID: 634150
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Slide1Slide2
Units of Counting
Dozen
Pair Gross Ream
12
2
144
500Slide3Slide4
Counting M&M’s
Example 1:How many M&M’s are in one party-sized bag?
Given on the bag… 1 bag = 1190.7g We want… # M&M’s per bag Slide5
Counting M&M’s
What other conversion factor do we need?
Remember we have these 1 bag = 1190.7g1 M&M = 0.85gSlide6
Counting M&M’s
We can even go backwards!
Example 2: We have 3.96 x 109 M&M’s. How many bags of M&M’s do we have when we’ve got 3.96 x 109 M&M’s? Keep your answer in scientific notation. Round to the nearest hundredth Slide7
Counting M&M’s
We can go one step farther with this!
Example 3: We have 3.96 x 109 M&M’s. How many grams of M&M’s do we have when we’ve got 3.96 x 109 M&M’s? Keep your answer in scientific notation. Round to the nearest hundredth Slide8
Counting M&M’s as an analogy
We counted 1400 M&M’s without physically counting them.
We counted M&M’s by mass.That is what chemists do with the number of particles in chemicals.Chemists count particles by mass. Slide9
Units of Counting
Dozen
Pair Gross Ream
Party-sized Bag Moles (abbreviated: mol
)
12
2
144
500
1400 M&Ms
6.022 x
10
23
particles
Simply a counting unit Slide10
Avogadro’s Number
Named after Italian scientist
Avogadro DID NOT discover Avogadro’s number His work paved the way to the discovery His work inspired other scientists to experiment on pure carbon-12
They found that there are 6.0221367 x 1023 atoms in exactly 12.0000g of pure carbon-12 Slide11
Avogadro’s Number
Definition: the number of particles in a mole.
This number is 6.022 x 1023Written as
6.022 x 1023 particles/
molIn the M&M analogy: 1400 M&Ms/bag Slide12
Molar Mass
The mass of one mole
Units are g/mol In the M&M analogy g/bagRound the atomic mass from the periodic table to the second decimal place