CHEM104 Lecture Chapter 1: Unit Conversions

Importance of Unit Conversions

• Essential skill in science classes
• Allows conversion between different units for calculations
  • Example: Volume in liters vs. measurements in milliliters

Dimensional Analysis

• Also known as:
  • Factor Label Method
  • Unit Factor Method
• Useful for performing unit conversions

Equalities in Unit Conversion

• Measurements that are equal but in different units
  • Example: 5 feet = 60 inches
• Equalities are the basis for conversion factors

Metric Prefixes

• Important prefixes to remember:
  • Kilo: means 1000
  • Centi: means one-hundredth
  • Milli: means one-thousandth
• Example Equalities:
  • 1 km = 1000 meters
  • 1 mg = 0.001 grams or 1 gram = 1000 mg

Tips for Using Equalities

• Bigger number goes with the smaller unit
• Examples:
  • Kilometer vs. Meter
  • Gram vs. Milligram

Conversion Factors

• Definition: An equality expressed as a ratio
• Examples:
  • 5 feet/60 inches
  • 1 foot/12 inches
• Important Note: Conversion factors are equal to 1, preserving measurement value

Performing Unit Conversions

• Write down original measurement
• Multiply by the proper conversion factor
• The unit to convert to goes on top, and the unit to cancel goes on the bottom

Example Conversions

1. Meters to Kilometers:

   • Convert 37.5 meters to kilometers
   • Use conversion factor: 1 km/1000 meters
   • Result: 0.375 kilometers

2. Centimeters to Inches:

   • Convert 10.0 centimeters to inches
   • Conversion factor: 1 inch/2.54 centimeters
   • Result: 3.93 inches

3. Using Density as a Conversion Factor:

   • Density of liquid mercury: 13.6 grams/milliliter
   • Find mass of 2.75 milliliters of mercury
   • Conversion factor: 13.6 grams/1 milliliter
   • Result: 37.4 grams

Resources

• Reference tables in textbooks or lab manuals
• Online resources for additional support

Conclusion

• Understanding and using unit conversions are crucial for accurate scientific calculations.
• Practice and familiarity with metric prefixes and conversion factors are key to mastering this skill.

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Remember to refer to your lab manual and textbook for more detailed tables and examples of conversion factors.