Significant Digits, Uncertainty, and Measurement in Chemistry

Vocabulary flashcards covering measurement types, uncertainty, significant figure rules, logarithms, accuracy, and precision.

Qualitative Descriptions

Descriptions in chemistry that refer to the identity or form of a substance present.

Quantitative Measurements

Experiments or measurements that determine the amount of a substance present.

Exact Numbers

Numbers that have defined values (such as $1\,\text{kg} = 1000\,\text{g}$ or $1\,\text{dozen} = 12\,\text{objects}$) or are determined by counting.

Inexact Numbers

Numbers measured by any method other than counting, such as length, mass, volume, time, and speed.

Significant Figures

The meaningful digits in a reported number.

Uncertain Digit

The last digit in a measured number, which is estimated to one digit beyond the smallest scale division.

Scientific Notation

A expression of a number consisting of a decimal part usually between 1 and 10, multiplied by an exponential part $10^n$.

Addition and Subtraction S.F. Rule

Rule stating that the answer cannot have more digits to the right of the decimal point than any of the original numbers.

Multiplication and Division S.F. Rule

Rule stating 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

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

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

Accuracy

A measure of how close a measurement is to the true value.

Precision

A measure of how close a series of replicate measurements are to one another, or as determined by the measuring device used.