Science · Scientific investigation
Scientific Measurement, Units, and Tools
Estimated time includes reading and one quiz. Take the time you need.
Start here: key ideas
- Use a tool that matches the quantity being measured.
- SI units make measurements easy to compare.
- Read one estimated digit beyond the smallest marked division when appropriate.
- Read the bottom of a water meniscus at eye level.
- Convert units by multiplying by conversion factors.
What you’ll be able to do
- Match quantities with tools and SI units.
- Read a marked scale and liquid meniscus.
- Tell accuracy from precision.
- Convert between metric units.
Choose measurement tools and SI units, read scales correctly, and convert between metric units.
Match tool, quantity, and unit
Choose a tool that measures the needed quantity. Use a ruler for length, a balance for mass, a graduated cylinder for liquid volume, a thermometer for temperature, and a stopwatch for time.
Common SI units include meter (m), kilogram (kg), second (s), kelvin (K), and liter (L) for common lab volume. Prefixes show powers of ten: kilo means 1,000; centi means 1/100; milli means 1/1,000.
Match the needed precision to the tool. A meter stick can measure a room, but a caliper may be better for a small diameter. A beaker can hold liquid but a graduated cylinder usually measures volume more precisely.
The liter is accepted for use with SI; the SI derived unit of volume is the cubic meter. A light microscope can view many living cells with suitable preparation; electron microscopes resolve much smaller structures but conventional electron-microscope preparation does not keep a sample alive.
Micro (µ) means one millionth, 10−6, of the base unit. A microliter (µL) is one millionth of a liter. Therefore 1,000 µL = 1 mL. Example: 2,500 µL × (1 mL / 1,000 µL) = 2.5 mL.
Volume examples: a submerged solid raises water from 20 to 27 mL, so its volume is 7 mL. For a rectangular solid, volume = length × width × height; use matching length units, giving cubic units.
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