Unit 1 Flashcards
Rules of Significant Figures (6)
- All non-zero digits - Significant
- Sandwich zeros - Significant
- Trailing zeros after decimal - Significant
- Zeros indicated with underline or decimal - Significant
- Trailing zeros before decimal - Not Significant
- Leading zeros after decimal - Not Significant
Precision
The relative proximity of a set of measurements to each other or how reproducible they are
For individual measurement – how many places to the right of the decimal are reported
Accuracy
How close measurements are to an “actual” value
Precision vs. Accuracy
Think of a target
If the measurements are close to the bullseye, they are accurate. If the measurements are clustered together, they are precise.
Measurements clustered together towards the edge of a target, therefore, are precise but NOT accurate.
Uncertainty in Measurements
Associated with any measured value due to instrument or equipment limitations
The reason why Sig Figs are significant! The uncertainty of a measurement lies in the last digit of a number
Level of uncertainty differs depending on the instrument or equipment used (±0.1cm, ±0.01cm, ±0.001cm…)
Uncertainty in Counted Quantities
There is none! They have infinite Sig Figs
Multiplying or Dividing Sig Figs
Answer must have the same number of sig figs as the LEAST precise measurement
Adding or Subtracting Sig Figs
Answer must have the same number of digits to the right of the decimal as the LEAST precise measurement
Exact numbers (Sig Figs)
Counted quantities
Exact conversions (°F = 1.8 °C + 32; °K = °C + 273.15)
–> Infinite number of Sig Figs!
Equation for converting °F –> °C
°F = 1.8 °C +32
Equation for converting °K –> °C
°K = °C + 273.15
Scientific notation
x.y × 10^x
Large quantities are expressed with a positive exponent, small quantities are expressed with a negative exponent
Metric Prefixes (expressed with base unit “g”)
1Mg = 106g
