1 / 16

Unit Conversions “Using Dimensional Analysis”

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.

eldora
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. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 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!

  2. “Picket Fence” Is a method to convert units. Examples include: Feet Inches Kilometers  Meters Kilograms  Grams

  3. 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

  4. Principle Behind Dimensional Analysis • You can multiply anything by 1 without changing the physical meaning.

  5. 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

  6. 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.

  7. All Equalities = 1 It doesn’t matter which is on top and which is on bottom. 1000 g 1 kg --------- = 1 or --------- = 1 1 kg 1000 g Both cancel out… and become 1.

  8. 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.

  9. 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

  10. 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

  11. 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

  12. Example: Convert 12.5 g to kg (1) 12.5 g 1 kg = 0.0125 kg 1000g (4) (3) (2) (5) Don’t forget the units

  13. See what happens without UNITS?!?!?

  14. Here’s a lady that talks really fast explaining dimensional analysis. • Dimensional Analysis Video Demostration

  15. Try: 18.2 km to m

  16. Try: How many centimeters are there in 5.54 inches?

More Related