IB Chem - Unit 1 (Measurements and Uncertainty)

analog device uncertainty

+-½ of the smallest increment

digital device uncertainty

+-exact smallest increment

analog

less precise type of tool for measurement

digital

more precise type of tool for measurement

error propagation

the uncertainties of 2 measurements combine when calculated

adding/subtracting (error propagation)

sum the uncertainties

multiplying/dividing (error propagation)

sum the percent uncertainties, convert to absolute uncertainty

absolute uncertainty

a measurement’s margin of error, expressed in the same unit as the measurement itself

percent uncertainty

a measurement’s margin of error, expressed in percent form (uncertainty/total measurement*100%)

density

mass/volume

uncertainties >2%

1 sig fig

uncertainties <2%

2 sig figs

not significant

right-end zeros (without decimal), left-end zeros

significant

all non-zeros, all zeros appearing between other non-zeros, right-end zeros (with decimal)

propagating uncertainty (strategy for multiplying/dividing)

1. Calculate result without UNC

2. Calculate %UNC for each measurement

3. Add %UNC together

4. Convert total %UNC back to absolute UNC

random error

variations as a result of equipment failure/error, not enough data, etc.

systematic error

variations as a result from improper procedure/design

percentage error

the calculation used to determine the accuracy of the measurement by comparing the experimental value to the actual/perceived value

listing absolute uncertainty

decimal place of the measurement coincides with the decimal place of the absolute uncertainty

experimental uncertainty

the range around the experimental value for which the actual value is likely to occur as a result of device fluctuations, calibration issues, or other problems involving the equipment/environment

calculated uncertainty

an estimate of a range wherein the actual value lies