Significant Digits, Measurement Uncertainty, and Precision

Flashcards defining key vocabulary terms related to measurements, uncertainty, scientific notation, significant figures, accuracy, and precision in chemistry.

Qualitative Description

A description in chemistry that refers to the identity or form of a substance present.

Quantitative Measurement

An experiment or measurement that determines the amount of a substance present.

Exact Number

A number that has a defined value (such as $1\,kg = 1000\,g$) or is determined by counting.

Inexact Number

A number measured by any method other than counting, such as length, mass, volume, time, or speed.

Significant Figures

The meaningful digits in a reported number.

Uncertain Digit

The last digit in a measured number, which is estimated between markings on a measuring tool and generally carries an uncertainty of $\pm 1$.

Scientific Notation

A format for writing numbers consisting of a decimal part (usually between 1 and 10) and an exponential part ($10$ raised to an exponent $n$).

Addition and Subtraction Rule for Significant Digits

A rule specifying that the calculated answer cannot have more digits to the right of the decimal point than any of the original numbers.

Multiplication and Division Rule for Significant Digits

A rule specifying that the number of significant figures in the final product or quotient is determined by the original number that has the smallest number of significant figures.

Logarithm Significant Digits Rule

A rule stating that the number of digits after the decimal point of $\log(x)$ should be equal to the number of significant figures of $x$.

Inverse Logarithm Significant Digits Rule

A rule stating that for an inverse log of $x$ ($10^x$), the number of significant figures in the answer is equal to the number of digits after the decimal point in $x$.

Accuracy

An indicator of how close a measurement is to the true value.

Precision

An indicator of how close a series of replicate measurements are to one another, or as determined by the measuring device in a single measurement.