Chapter 2: Measurements and Calculations

Flashcards generated from lecture notes on Measurements and Calculations, covering units of measurement, derived units, specific gravity, metric prefixes, conversions, uncertainty in measurement, precision and accuracy, types of error, significant figures, scientific notation, operations with units, and direct/inverse proportions.

Measurement

Quantitative observation consisting of 2 parts: a number and a scale (unit).

Derived Units

Units derived using measured units (e.g., density calculated from mass and volume).

Liter

A non-SI unit of volume commonly used, where 1 liter = 1 cubic decimeter = 1000 mL = 1000 cm3.

Specific Gravity (SG)

Ratio of a substance's density to the density of water at a specified temperature and pressure; a dimensionless quantity.

Factor-Label Method (Dimensional Analysis)

Problem-solving method using conversion factors to change units.

Uncertainty in Measurement

A digit that must be estimated in a measurement, reflecting the inherent uncertainty.

Accuracy

Agreement of a particular value with the true value.

Precision

Degree of agreement among several measurements made in the same manner.

Random Error (Indeterminate Error)

Measurement has an equal probability of being high or low.

Systematic Error (Determinate Error)

Occurs in the same direction each time (high or low), often resulting from poor technique or incorrect calibration.

Percent Error

A way to compare the accuracy of an experimental value with an accepted value.

Significant Figures (Sig Figs)

Digits in a number that are known with certainty plus one uncertain digit.

Leading Zeros

Zeros that come before the first nonzero number; do not count as sig figs.

Captive Zeros

Zeros in between two nonzero numbers; count as sig figs.

Trailing Zeros

Zeros that have no nonzero numbers after them; count as sig figs only if they are to the right of the decimal point.

Exact Numbers

Numbers not obtained through measurement but by definition or counting; have an infinite number of significant figures.

Scientific Notation

A method of representing very large or very small numbers using powers of 10.

Direct Proportions

The quotient of two variables is a constant (k = y/x); as one increases, the other increases.

Inverse Proportions

The product of two variables is a constant (k = xy); as one increases, the other decreases.