Chapter R: Measurement and Calculations in Chemistry Flashcards

Vocabulary practice cards reviewing essential concepts from Chapter R including units, sig figs, dimensional analysis, density, state changes, classification of matter, energy, and the mole.

Quantitative Observation

A measurement consisting of two parts: a numerical value and a scale or unit.

Fundamental SI Units

The standard set of base units established in the International System of Units, including the kilogram ($kg$) for mass, meter ($m$) for length, second ($s$) for time, kelvin ($K$) for temperature, ampere ($A$) for electric current, and mole ($mol$) for amount of substance.

SI Prefix

A prefix attached to an SI unit to indicate a power-of-ten multiplier that changes the size of the unit (such as kilo- for $10^{3}$ or milli- for $10^{-3}$).

Uncertain Digit

The final digit recorded in a scientific measurement that must be estimated based on the measuring device.

Meniscus

The curved bottom of the liquid surface in a volumetric instrument (such as a buret or graduated cylinder) at which volume readings are taken.

Accuracy

The degree of agreement between a measured value and the true or accepted value.

Precision

The degree of agreement among several repeated measurements of the same quantity.

High Accuracy and High Precision

A measurement outcome where values are both closely grouped together and centered on the true value.

Low Accuracy and Low Precision

A measurement outcome where values are widely scattered and far from the true target value.

Low Accuracy and High Precision

A measurement outcome where values are clustered closely together but consistently offset from the true value.

Leading Zeros

Zeros that precede all non-zero digits in a number; they never count as significant figures.

Captive Zeros

Zeros located between non-zero digits in a number; they always count as significant figures.

Trailing Zeros

Zeros located at the right end of a number; they count as significant figures only if the number contains a written decimal point.

Exact Numbers

Numbers obtained by counting or by precise definition that possess an infinite number of significant figures.

Multiplication and Division Rule for Significant Figures

The principle that the result of a multiplication or division calculation must contain the same number of significant figures as the least precise measurement used.

Addition and Subtraction Rule for Significant Figures

The principle that the result of an addition or subtraction calculation must have the same number of decimal places as the least precise measurement used.

Dimensional Analysis

A system of problem solving that converts a measurement from one unit to another using equivalence statements and unit factors.

Celsius to Kelvin Conversion

The formula used to convert temperature from Celsius to Kelvin, given by $T_K = T_C + 273.15$.

Fahrenheit to Celsius Conversion

The formula used to convert temperature from Fahrenheit to Celsius, given by $T_C = (T_F - 32^\text{o}F) \frac{5^\text{o}C}{9^\text{o}F}$.

Temperature Scale Equivalence Point

The specific temperature at which the Celsius and Fahrenheit scales read identical numeric values, which occurs at $-40^\text{o}C = -40^\text{o}F$.

Density

The mass of a substance per unit volume, defined by the formula $x=\frac{\text{mass}}{\text{volume}}$ with typical units of $g/cm^3$ or $g/mL$.

Solid

A state of matter that is rigid and maintains a fixed volume and a fixed shape.

Liquid

A state of matter that maintains a definite volume but takes on the shape of its container.

Gas

A state of matter that has no fixed volume or shape, expanding to fill both the shape and volume of its container.

Homogeneous Mixture

A mixture with visibly indistinguishable parts that has uniform composition throughout, also referred to as a solution.

Heterogeneous Mixture

A mixture with visibly distinguishable parts containing regions with different properties.

Physical Change

A change in the physical form or state of a substance that does not alter its chemical composition.

Chemical Change

A reaction in which one or more substances are converted into entirely new substances with different chemical compositions and properties.

Organization of Matter

The classification scheme dividing matter into mixtures or pure substances, and further into heterogeneous/homogeneous mixtures and elements/compounds.

Law of Conservation of Energy

The principle stating that energy can be converted from one form to another but cannot be created or destroyed, keeping the total energy of the universe constant.

Work

Force acting over a distance.

Heat

Energy transferred between objects as a result of a temperature difference between them.

Kinetic Energy

Energy associated with the motion of an object.

Potential Energy

Stored energy resulting from an object's position or chemical composition.

Mole

The fundamental SI unit used to count chemical entities, equal to Avogadro's number ($6.022 \times 10^{23}$ particles).