Measurements and Sig Figs Pt. 2

These flashcards cover key concepts on how to correctly treat numbers, specifically relating to measurements, significant figures, and rounding rules in the context of chemistry.

Exact Number

A quantity that is counted or defined, having no uncertainty (e.g., 12 eggs, 1,000 meters in a kilometer).

Measured Number

A quantity obtained by measurement using an instrument, which includes some degree of uncertainty (e.g., weight on a balance, length with a ruler).

Significant Figures

Digits in a measured number that include all known digits plus one estimated digit, representing the precision of the measurement.

Estimated Digit

The last digit in a measured number that is not known precisely, representing a level of uncertainty in the measurement.

Rounding

The process of adjusting the digits in a number based on significant figures or decimal places after performing calculations.

Multiplication / Division Rule

When multiplying or dividing two measured numbers, round the result to the least number of significant figures in any of the factors.

Addition / Subtraction Rule

When adding or subtracting measured numbers, round the result to the least number of decimal places among the numbers involved.

Meniscus

The curve at the surface of a liquid in a graduated cylinder that should be read at eye level to determine the volume accurately.

Nonzero Digits Rule

All nonzero digits in a number are always considered significant.

Sandwiched Zero Rule

Any zero that is between two significant digits is significant.

Trailing Zero Rule (Decimal)

Trailing zeros in a decimal number are significant if they are to the right of a nonzero digit.

Trailing Zero Rule (Whole Numbers)

Trailing zeros in whole numbers without a decimal are not considered significant.

Units in Measurements

All measurements must include units to convey the scale and context of the value represented.