CHEM 111: General Chemistry I - Measurement and Error Analysis

Vocabulary practice flashcards covering fundamental SI and metric units, conversions, laboratory glassware, concentration expressions, measurement uncertainty, significant figures, and basic statistics for CHEM 111 General Chemistry I.

Système International d’Unités (SI Units)

The international metric system of units established as fundamental base units from which all other scientific measurement units are derived.

Kilogram ($\text{kg}$)

The SI base unit of mass, equal to $1000\,\text{g}$.

Meter ($\text{m}$)

The SI base unit of length, used to measure distance.

Kelvin ($\text{K}$)

The SI base unit of temperature, which is written without a degree symbol and has its zero point at absolute zero.

Absolute Zero

The zero point on the Kelvin scale ($0\,\text{K}$, or $-273.15\,^\circ\text{C}$), representing nature's lowest possible temperature.

Mole ($\text{mol}$)

The SI base unit used to measure the amount of substance.

Angstrom ($\text{Å}$)

A non-SI metric unit commonly used to measure length in chemistry, defined as $1\,\text{Å} = 0.1\,\text{nm} = 10^{-10}\,\text{m}$.

Atomic Mass Unit ($\text{u}$ or $\text{amu}$)

A non-SI metric unit of mass used in chemistry, where $1\,\text{u} = 1.66054 \times 10^{-27}\,\text{kg}$.

Liter ($\text{L}$)

A metric unit of volume defined as the volume of a $1\,\text{decimeter}$ cube ($1\,\text{dm}^3$), equal to $1000\,\text{cm}^3$ or $1000\,\text{mL}$.

Density

An intensive physical property of a substance calculated as mass divided by volume ($\text{Density} = \frac{\text{mass}}{\text{volume}}$), commonly expressed in $\text{g/mL}$ or $\text{g/cm}^3$.

Exact Numbers

Numbers that are counted directly or fixed by definition (such as $12$ eggs in $1$ dozen), possessing no uncertainty.

Inexact Numbers

Numbers obtained by measurement whose values are subject to inherent uncertainty and equipment limitations.

Burette

A graduated glass tube fitted with a stopcock valve used in laboratories to deliver variable, precisely controlled volumes of liquid.

Volumetric Flask

A calibrated laboratory flask designed to contain a specific, exact volume of liquid when filled to the calibration line.

Pipette

A calibrated laboratory instrument designed to deliver an exact, specified volume of liquid.

Molarity ($c$)

A concentration unit defined as the number of moles of solute per liter of solution ($\text{mol/L}$).

Molality ($m$)

A concentration unit defined as the number of moles of solute per kilogram of solvent.

Weight Percent (wt%)

A measure of concentration defined as $\frac{\text{mass of solute}}{\text{mass of total solution or mixture}} \times 100$.

Specific Gravity

The dimensionless ratio of the density of a substance to the density of water at $4\,^\circ\text{C}$.

Parts per Million (ppm)

A concentration unit for trace quantities defined as $\frac{\text{mass of substance}}{\text{mass of sample}} \times 10^6$, equivalent to $1\,\mu\text{g/mL}$ or $1\,\text{mg/L}$ in dilute aqueous solutions.

Parts per Billion (ppb)

A concentration unit for trace quantities defined as $\frac{\text{mass of substance}}{\text{mass of sample}} \times 10^9$, equivalent to $1\,\text{ng/mL}$ or $1\,\mu\text{g/L}$ in dilute aqueous solutions.

Systematic Error (Determinate Error)

An experimental error having a definite size and sign (bias) caused by faults in the instrument, method, or analyst that can be detected and eliminated.

Random Error (Indeterminate Error)

An unavoidable error arising from limitations in measurement ability and chance environmental fluctuations that has an equal probability of being positive or negative and can be reduced by averaging replicates.

Accuracy

The proximity or nearness of a measured value to the true or accepted value of a quantity.

Precision

The agreement or closeness of several repeated measurements of the same quantity to each other, indicating reproducibility.

Significant Figures

The measured digits in a numerical value, representing the minimum number of digits needed to write the value in scientific notation without loss of accuracy.

Scientific Notation

A system of expressing numbers as a value between $1$ and $10$ multiplied by an appropriate power of $10$, providing an unambiguous representation of significant digits.

Absolute Uncertainty

The margin of uncertainty associated with a measurement, expressed in the same units as the measurement itself.

Relative Uncertainty

The dimensionless ratio comparing the absolute uncertainty of a measurement to the magnitude of the measurement ($\text{R.U.} = \frac{\text{absolute uncertainty}}{\text{magnitude of measurement}}$).

Mean ($\bar{x}$)

The arithmetic average representing the center of a data distribution, calculated as the sum of measured values divided by the number of measurements ($n$).

Median

The middle value in a set of measurements ordered from least to highest.

Range

The difference between the highest and lowest recorded values in a series of measurements.

Standard Deviation ($s$)

A statistical measure of the dispersion or width of a distribution, calculated as $s = \sqrt{\frac{1}{n-1}\sum_{i=1}^n (x_i - \bar{x})^2}$.

Variance ($s^2$ or $\sigma^2$)

A statistical quantity measuring how data points differ from the mean, defined as the average of squared deviations or the square of the standard deviation.

Empirical Rule (68-95-99.7 Rule)

A rule for bell-shaped normal distributions stating that approximately $68\%$ of values fall within $1$ standard deviation of the mean, $95\%$ within $2$, and $99.7\%$ within $3$.