Ch 4 Dimensional Analysis
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This document discusses dimensional analysis and conversion factors for converting between different units of measurement. It provides examples of converting between units like inches and centimeters, hours and minutes, meters and kilometers. It emphasizes setting up conversion factors so that the initial and final units cancel out properly. Finally, it lists some common conversion factors between English and metric units like grams to pounds, centimeters to inches, and liters to quarts.
Ch 4 Dimensional Analysis
- 1. DIMENSIONAL ANALYSIS MHS Chemistry Chapter 4
- 2. Conversion Factors Fractions in which the numerator and denominator are EQUAL quantities expressed in different units Example : 1 in. = 2.54 cm Factors: 1 in. and 2.54 cm 2.54 cm 1 in.
- 4. How many minutes are in 2.5 hours ? Conversion factor 2.5 hr x 60 min = 150 min 1 hr cancel By using dimensional analysis / factor-label method, the UNITS ensure that you have the conversion right side up, and the UNITS are calculated as well as the numbers!
- 5. Sample Problem You have $7.25 in your pocket in quarters. How many quarters do you have? 7.25 dollars 4 quarters 1 dollar X = 29 quarters
- 6. Learning Check Write conversion factors that relate each of the following pairs of units: 1. Liters and mL 2. Hours and minutes 3. Meters and kilometers
- 7. Learning Check A rattlesnake is 2.44 m long. How long is the snake in cm? a) 2440 cm b) 244 cm c) 24.4 cm
- 8. Learning Check How many seconds are in 1.4 days? Unit plan : days hr min seconds 1.4 days x 24 hr x ?? 1 day
- 9. Wait a minute! What is wrong with the following setup? 1.4 day x 1 day x 60 min x 60 sec 24 hr 1 hr 1 min
- 10. English and Metric Conversions If you know ONE conversion for each type of measurement, you can convert anything! You must memorize and use these conversions: Mass: 454 grams = 1 pound Length: 2.54 cm = 1 inch Volume: 0.946 L = 1 quart
- 11. Learning Check An adult human has 4.65 L of blood. How many gallons of blood is that? Unit plan : L qt gallon Equalities: 1 quart = 0.946 L 1 gallon = 4 quarts Your Setup:
- 12. Solution Unit plan : L qt gallon Setup: 4.65 L x 1 qt x 1 gal = 1.23 gal 0.946 L 4 qt
- 13. Steps to Problem Solving Read problem Identify data Make a unit plan from the initial unit to the desired unit Select conversion factors Change initial unit to desired unit Cancel units and check Do math on calculator Give an answer using significant figures
- 14. Dealing with Two Units – Pre-AP Only If your pace on a treadmill is 65 meters per minute, how many seconds will it take for you to walk a distance of 8450 feet? 8450 ft 1m 1 min 60 sec 1 3.28 ft 65m 1 min