CHAPTER 1: MEASUREMENTS Flashcards
UNIT
standard for comparison
MOST COMMON UNIT SYSTEMS
metric and imperial
SI UNITS
international system of units; used by scientists and based on metric system
Length Mass Time Temperature Amount of substance Current
meter (m) kilogram (kg) second (s) kelvin or celsius (K or C) mole (mol) ampere (amp)
VOLUME
- the amount of space occupied by an object
- SI unit is m3, derived from base unit of meters
- other common units for volume are liter (L) and milliliter (mL)
DENSITY
- the ratio of the mass of sample to its volume; mass/volume
- mass per unit volume
- g/cm^3; g/mL; g/L
- density can be used as a conversion factor to go from the mass of a sample to the volume it occupies, or vice versa
DIMENSIONAL ANALYSIS
(also, factor-label method) versatile mathematical approach that can be applied to computations ranging from simple unit conversions to more complex, multi-step calculations involving several different quantities
ABSOLUTE ZERO
lowest temperature that theoretically can be achieved
-273.15°C, 0.00 K, -459.67°F
EXACT NUMBER
- Counting is the only type of measurement that is free from uncertainty
- Defined quantities are exact
SIGNIFICANT FIGURES
any non zero number
zeros in between non zero numbers
trailing zeros where there is no decimal point are ambiguous; use scientific notation to avoid ambiguity
50,060.00 has 7 significant figures
zeros the left of non zero number are leading numbers and are not significant
zeros after non zero numbers and after decimal point
represent uncertainty; show how precise a number is
SIGNIFICANT FIGURES: ADDITION/SUBTRACTION
Result depends upon the value with the least number of decimal places
SIGNIFICANT FIGURES: MULTIPLICATION/DIVISION
Result depends upon the value with the least number of significant digits
ACCURACY
actual; measurements yield results close to the true or accepted value
PRECISION
reproducible; measurements yield similar results when repeated
SCIENTIFIC NOTATION
want a number that is between 1 and 10
