Unit3-DimensionalAnalysis.ppt

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Dimensional Analysis

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SI Units

• _{Universally applied standards of measure}

– _{meter (m) – Length} – _{gram (g) – Mass}

– _{Mole (mol) – Amount of a Substance} – _{Kelvin (K) – Temperature}

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SI Unit Prefixes

• _{There are the ones I need you to know!!}

– _{Base (meter, liter, gram, second)} – _{Kilo – 1000}

– _{Centi – 1/100}th

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SI Unit Comparison

• _{Liter (L) vs. Milliliter (mL)}

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Equalities

• _{Equalities take on the following form:} 4 quarters = 1 dollar

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Conversion Factors

• _{These equalities can be then written as} conversion factors.

4 quarters = 1 dollar

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Conversion Factors

• _{Try Some!!}

– _{Write the equality between liters and milliliters.} – _{Write the TWO conversion factors that you can}

derive from the equality above.

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Unit Conversions

• _{Now that we understand what a conversion}

factor is, we can convert between units easily using a conversion bridge!!

• _{The best way to understand this is to JUMP}

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Unit Conversions

• _{These are the GOLDEN RULES of Conversion!!}

– _{UNDERLINE all given information!} – _{BOX the units that are needed!}

– _{Set up the conversion bridge so that the GIVEN}

information is in the upper left hand side of the conversion bridge and the UNITS FOR WHAT YOU NEED are in the upper right hand corner!

– _{Insert UNITS so that the UNWANTED UNITS CANCEL}

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LET’s JUMP IN!

• _{The best way to learn to solve these}

conversions is to simply TRY IT!!

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LET’s JUMP IN!

• _{UNDERLINE WHAT IS GIVEN!}

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LET’s JUMP IN!

• _{BOX THE UNITS OF WHAT IS NEEDED!}

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LET’s JUMP IN!

• _{Set up the conversion bridge so that the GIVEN information is in}

the upper left hand side of the conversion bridge and the UNITS FOR WHAT YOU NEED are in the upper right hand corner!

• _{Convert 130 mm to meters!}

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LET’s JUMP IN!

• Insert UNITS so that the UNWANTED UNITS CANCEL DAIGONALLY and so

the proper CONVERSION UNITS are inserted in the correct orientation.

•_{Convert 130 mm to meters!}

130 mm 1 meters

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LET’s JUMP IN!

• _{Multiply everything on TOP TOGETHER and DIVIDE by}

the FIGURES on the BOTTOM!

130 mm 1 meters

1000 mm

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LET’s JUMP IN!

• _{PAY CLOSE ATTENTION TO SIG FIGs and UNITS!! If}

you forget these things, your solution may be marked INCORRECT!! AHHH!

0.13 meters

130 mm 1 meters

1000 mm

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ATOMS/MOLECULES to MOLES

• _{We can convert between ATOMS/MOLECULES}

and MOLES or MOLES and ATOMS/MOLECULES by using AVOGADRO’s NUMBER!

• _{AVOGADROS NUMBER = 6.02 X 10}23_particles

• _{PARTICLES of CHEMISTRY = Atoms and}

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ATOMS/MOLECULES to MOLES

6.02 X 10

23

of anything = 1

mol

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MOL FUN FACTS!

One mole of paper would make a stack that would reach to the moon more than 80 billion times.

A one liter bottle of water contains 55.5 moles of water

One mole of seconds is about 19

quadrillion years, 4,240,666 times the age of the earth, or 954,150 times the age of the universe itself

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ATOMS/MOLECULES to MOLES

In Chemistry the important fact is:

1 mol = 6.02 X 1023

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ATOMS/MOLECULES to MOLES

• _{Convert 5.43 X 10}23_{atoms to moles!}

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ATOMS/MOLECULES to MOLES

• _{UNDERLINE what is GIVEN!}

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ATOMS/MOLECULES to MOLES

• _{BOX THE UNITS of what is NEEDED!}

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ATOMS/MOLECULES to MOLES

• _{Set up the conversion bridge so that the GIVEN}

•_{Convert 5.43 X 10}23_{atoms to moles!}

5.43 X 1023_atoms

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ATOMS/MOLECULES to MOLES

– _{Insert UNITS so that the UNWANTED UNITS CANCEL}

DAIGONALLY and so the proper CONVERSION UNITS are inserted in the correct orientation.

•_{Convert 5.43 X 10}23_{atoms to moles!}

5.43 X 1023_atoms

moles

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ATOMS/MOLECULES to MOLES

• _{Multiply everything on TOP TOGETHER and}

DIVIDE by the FIGURES on the BOTTOM!

5.43 X 1023_atoms

moles

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ATOMS/MOLECULES to MOLES

• _{PAY CLOSE ATTENTION TO SIG FIGs and}

UNITS!! If you forget these things, your

solution may be marked INCORRECT!! AHHH!

5.43 X 1023_atoms

moles

6.02 X 1023_atoms 1

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Try THESE!!

• _{Pay close attention! Conversion factors can be}

flipped to suit the question being asked!! DO YOU NEED TO FLIP YOUR CONVERSION

FACTORS!?

• _{Convert 3.442 X 10}24_{atoms to moles.}

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Mass to Moles

• _{We can find a conversion factor that allows us to} covert from Mass (GRAMS) to Moles using out periodic table!

• _{This conversion factor is known as the MOLAR} MASS!

• _{It has the UNITS grams/mol!}

• _{You all already know how to find the MOLAR}

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Mass to Moles

• _{The ONLY difference between the}

ATOMIC/MOLECULAR MASS and the MOLAR MASS is the UNITS!!

• _{Change AMU to g/mol!}

• _{This way…we can just write our conversion}

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Moles to Mass

• _{Let’s TRY!}

• _{Convert 3.4 grams of Iron (Fe) to moles.}

• _{Again…UNDERLINE WHAT WE are GIVEN and}

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Moles to Mass

• _{Set up the conversion bridge so that the GIVEN}

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Moles to Mass

• _{Insert UNITS so that the UNWANTED UNITS CANCEL}

DAIGONALLY and so the proper CONVERSION UNITS are inserted in the correct orientation.

•_{Convert 3.4 grams of Iron (Fe) to moles.}

3.4 grams Fe 1 Mol Fe

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Moles to Mass

• _{Multiply everything on TOP TOGETHER and} DIVIDE by the FIGURES on the BOTTOM!

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Moles to Mass

• _{PAY CLOSE ATTENTION TO SIG FIGs and} UNITS!! If you forget these things, your

solution may be marked INCORRECT!! AHHH!

55.85 grams Fe

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Try THESE!!

• _{How many grams are there in 4.4 moles of}

Gold?

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NOW…3 STEPS!

• _{Identify 3 step requirements when there are:}

– _{Conversions from GRAMS to MOLECULES/ATOMS} – _{Conversions from MOLECULES/ATOMS to GRAMS}

– _{Be sure you know how to identify when to use}

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NOW…3 STEPS!

• _{Convert 3.2 X 10}24 _{atoms Lithium to grams.}

• _{The rules are the same!!} • _{The steps are the same!!}

• _{I’m just going to need a larger BRIDGE!}

3.2 X 1023_{atoms Fe} grams Fe

1 mol Fe

1 mol Fe 6.94

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NOW…3 STEPS!

• _{Convert 3.2 X 10}24 _{atoms Lithium to grams.}

• _{Cancel the proper units!!}

• _{Multiply and Divide properly!!} • _{There you go!}

3.2 X 1023_{atoms Fe} grams Fe

1 mol Fe

1 mol Fe 6.94

6.02 X 1023_{atoms Fe}

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Try THESE!

• Convert 4.5 grams of CaCl₂ to molecules.

• _{How much will 6.2 X 10}24_{molecules of CO}

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Things to Remember!

• _{Conversion Factors can flip as needed!}

• _Remember

– _{6.02 X 10}23_{will ALWAYS go next to}

ATOMS/MOLECULES.

– _{The MOLAR MASS will ALWAYS be written next to}

the grams (g) units.

– _{For this unit…ALWAYS write 1 next to the Mol}