Overview
This lecture explains the main metric units of length, how to convert between them, and provides size examples of microscopic and everyday objects.
Metric Units of Length
- Key units: nanometer (nm), micrometer (µm), millimeter (mm), centimeter (cm), meter (m), kilometer (km).
- Each unit is 1,000 times larger or smaller than the next (except for centimeters: 1 cm = 10 mm; 100 cm = 1 m).
Converting Between Units
- To convert to a larger unit, divide by 1,000 for each step up (e.g., mm to m: 6 mm ÷ 1,000 = 0.006 m).
- To convert to a smaller unit, multiply by 1,000 for each step down (e.g., 6 mm × 1,000 = 6,000 µm).
- For non-adjacent units, repeat the divide/multiply process for each step, or calculate the total factor.
- For centimeters, convert to millimeters by multiplying by 10, then proceed up or down the scale as needed.
Example Conversions
- 6 mm = 0.006 m = 0.000006 km = 6,000 µm = 6,000,000 nm.
- 340 nm = 0.34 µm = 0.00034 mm.
- 30 cm = 300 mm = 300,000 µm = 300,000,000 nm.
Sizes of Common Objects
- Atoms: 0.1–0.5 nm wide.
- Small molecules (glucose): ~1 nm across.
- Viruses: ~100 nm wide.
- Bacteria: ~1 µm across.
- Animal/plant cells: 10–100 µm wide.
- Human hair: ~100 µm wide.
- Human eye sees down to ~100 µm; light microscopes reach ~500 nm; electron microscopes see ~0.1 nm.
Key Terms & Definitions
- Nanometer (nm) — 1 billionth of a meter (1 nm = 1 x 10⁻⁹ m).
- Micrometer (µm) — 1 millionth of a meter (1 µm = 1 x 10⁻⁶ m).
- Millimeter (mm) — 1 thousandth of a meter (1 mm = 1 x 10⁻³ m).
- Centimeter (cm) — one hundredth of a meter (1 cm = 1 x 10⁻² m).
- Meter (m) — base unit of length in the metric system.
- Kilometer (km) — 1,000 meters (1 km = 1 x 10³ m).
Action Items / Next Steps
- Practice conversion questions and review lesson materials on the provided learning platform.