Unit conversions using dimensional analysis
This presentation is the property of its rightful owner.
Sponsored Links
1 / 16

Unit Conversions “Using Dimensional Analysis” PowerPoint PPT Presentation


  • 160 Views
  • Uploaded on
  • Presentation posted in: General

Unit Conversions “Using Dimensional Analysis”. We call this the “Picket Fence” method to convert units (the book calls it the Factor-Label method to convert from one unit to another. (pg. 130-134 in text) Units are our friends, really!. “Picket Fence”. Is a method to convert units.

Download Presentation

Unit Conversions “Using Dimensional Analysis”

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Unit conversions using dimensional analysis

Unit Conversions“Using Dimensional Analysis”

We call this the “Picket Fence” methodto convert units

(the book calls it the Factor-Label method to convert from one unit to another. (pg. 130-134 in text)

Units are our friends, really!


Picket fence

“Picket Fence”

Is a method to convert units.

Examples include:

Feet Inches

Kilometers  Meters

Kilograms  Grams


Why is dimensional analysis important

Units are constantly needing to be converted throughout chemistry.

Stoichiometry (the relationship between quantities of reactants and products in a chemical reaction) problems depend on it.

Why is Dimensional Analysis Important


Principle behind dimensional analysis

Principle Behind Dimensional Analysis

  • You can multiply anything by 1 without changing the physical meaning.


How do we multiply by 1

How Do We Multiply By 1

If the same thing is on the top and the bottom of a fraction,

= 1

Then they cancel out… and become 1


All equalities 1

All Equalities = 1

Any time you put two things that are equal to each other

1000g = 1kg

On top and on bottom

1000 g

--------- = 1

1 kg

Then they cancel out… and become 1.


All equalities 11

All Equalities = 1

It doesn’t matter which is on top and which is on bottom.

1000 g1 kg

--------- = 1 or --------- = 1

1 kg1000 g

Both cancel out… and become 1.


Unit conversions using dimensional analysis

1 km = 1000 m (A metric equality)

Any equality can be written two ways (conversion factors)

1000 m=1 km= 1

1 km 1000 m

Which one to use?

Depends on which direction you are trying to go.


The rules

The Rules

  • Write down “given” + unit

  • Draw a horizontal & vertical line “picket fence”

  • Write “wanted” / “given” on the fence

  • Enter proper #s for “wanted units & “given” units

  • Cancel units & do the math


Unit conversions using dimensional analysis

For example: Convert 25 km to meters

Use the conversion factor that allows units to cancel.

1000 mor 1 km

1 km 1000 m

“given” unit

=“want” unit

picket

fence


Unit conversions using dimensional analysis

For example: Convert 25 km to meters (m)

Use the conversion factor that allows units to cancel.

1000 m

1 km

25 km 1000 m= 25000 m (or 2.5 x 104 m)

1 km

Just a little

Scientific

notation

picket

fence

“given”conversion‘want’

factor


Example convert 12 5 g to kg

Example: Convert 12.5 g to kg

(1)

12.5 g1 kg

= 0.0125kg

1000g

(4)

(3)

(2)

(5)

Don’t forget the units


Unit conversions using dimensional analysis

See what happens without

UNITS?!?!?


Unit conversions using dimensional analysis

  • Here’s a lady that talks really fast explaining dimensional analysis.

    • Dimensional Analysis Video Demostration


Try 18 2 km to m

Try: 18.2 km to m


Try how many centimeters are there in 5 54 inches

Try: How many centimeters are there in 5.54 inches?


  • Login