General Chemistry I: Significant Figures and Metric Conversions

General Chemistry I – Metric to Metric Conversions and Significant Figures (Lecture Notes)

  • Topics overview

    • Brief recap of topics overlapping with basic/high school chemistry and ALEKS reviews
    • Topics to refresh for General Chemistry I, especially if labs are involved
    • Chemical and physical properties and changes
    • States of matter
    • Rules for significant figures and rounding
    • Temperature scales: Celsius, Fahrenheit, Kelvin (Kelvin is an absolute temperature scale)
    • Emphasis on metric-to-metric conversions; quick refresher on metric prefixes and common conversions
    • Also mention metric-to-standard (English) conversions as practical context (length, volume, mass), with common conversion benchmarks

  • Important note on a potential typo in the transcript

    • The transcript states, “one kilometer is 1,000 liters.” The correct relation is: one kilometer equals 1,000 meters. (Exact conversions like 1 L = 1,000 mL are correct; this is metric-to-metric.)

  • Quick reference: units, properties, and common conversions

    • States of matter and phase properties (brief mention; refresh as needed)
    • Distinguish between chemical properties, physical properties, and physical changes
    • Temperature scales: extoC,extoF,K^ ext{o}C, ^ ext{o}F, K (Kelvin is absolute; no degree symbol)
    • Common household and lab conversion anchors (examples listed below)
    • Length: inches to centimeters (example factor to know)
    • Volume: milliliters to quarts
    • Mass: pounds to grams
    • Daily-use defaults: 12 inches = 1 foot; 3 feet = 1 yard; 4 quarts = 1 gallon; 2 pints = 1 quart; 1 pint = 1 cup; 16 ounces = 1 pound (these last are practical daily benchmarks)

  • Metric prefixes and their powers of ten (key prefixes touched on in the lecture)

    • Common prefixes and their factors (for quick recall):
    • kilo (k): 10310^{3}
    • deci (d): 10−110^{-1}
    • centi (c): 10−210^{-2}
    • milli (m): 10−310^{-3}
    • micro (µ): 10−610^{-6}
    • nano (n): 10−910^{-9}
    • pico (p): 10−1210^{-12}
    • Also discussed in context of unit conversions:
    • Length examples: 1 kilometer = 10^3 meters (note: transcript mentions other units like liters by mistake; correct is meters)
    • Volume examples: 1 liter = 1000 milliliters
    • Mass examples: 1 gram = 1000 milligrams
    • Additional, smaller prefixes mentioned for very small scales (angstroms, etc.)
    • Exact versus measured: some conversions are exact (within same measurement system or defined exactly by convention), others are measured or defined across systems

  • Exact numbers vs measured numbers (concepts emphasized in the lecture)

    • Measured numbers: obtained with a measuring device (e.g., length with a ruler, speed with a speedometer)
    • Exact numbers: counting quantities or defined conversion factors within the same measurement system
    • Examples from the lecture:
      • 1 inch = 2.54 cm — exact (defined conversion, infinite sig figs)
      • 1 L = 1000 mL — exact (metric-to-metric)
      • Counting examples (infinite sig figs): 800 atoms (counted) or 4,500 grains (counted) – exact
      • 1 yd = 0.9144 m — not exact for the English-to-metric direction in practice (conversion is defined, but the measured context is critical). The focal point is whether the conversion factor is exact or a measured quantity.
      • 1 lb = 454 g — not exact (English-to-metric conversion is approximate in practice)

  • How to determine significant figures (rules recap with examples)

    • Leading zeros are not significant (zeros to the left of the first nonzero digit)
    • Captive zeros are significant (zeros between nonzero digits)
    • Trailing zeros are significant only if a decimal point is shown or the number is in scientific notation
    • In scientific notation, all digits in