Chapter 1 Vocabulary: Numbers, Sig Figs, and SI Units

A set of vocabulary flashcards covering key terms from Chapter 1, including exact vs. measured numbers, significant figures, rounding rules, SI units and prefixes, density, volume, and dimensional analysis.

Exact numbers

Defined quantities with no uncertainty (known with certainty), such as counting objects or defined relationships like 12 inches in a foot.

Measured numbers

Numbers obtained from measurement that include some uncertainty due to instrument precision and reading or user interpretation.

Uncertainty

The doubt in a measurement’s exact value, arising from instrument precision, calibration, and how the user reads the data.

Significant figures (sig figs)

Digits in a measured value that convey its precision: all digits known with certainty plus one uncertain digit; exact numbers have unlimited sig figs and do not limit measurements.

SF (abbreviation for significant figures)

Common shorthand for significant figures used in reporting measurements.

Leading zeros

Zeros that appear before the first nonzero digit; they are not significant.

Captive zeros

Zeros between two nonzero digits; they are significant.

Trailing zeros (no decimal point)

Zeros at the end of a number with no decimal point; generally not significant.

Trailing zeros (with decimal point)

Trailing zeros after a decimal point are significant.

Decimal point rule

Presence of a decimal point makes trailing zeros significant; without a decimal, trailing zeros may not be significant.

Scientific notation (coefficients)

All digits in the coefficient are significant; helps control sig figs in calculations.

Exact numbers and sig figs

Exact numbers have unlimited sig figs and do not constrain the number of sig figs in a calculation.

Rounding

Process of adjusting a number to the appropriate precision: drop digits and decide whether to round up or keep; use extra figures to improve accuracy.

Rounding rule (sig figs)

If the dropped digit is less than 5, keep the last retained digit; if greater than 5, round up (following standard rounding rules).

Multiplication/Division sig figs rule

The result should have as many sig figs as the factor with the fewest sig figs among the inputs.

Addition/Subtraction sig figs rule

The result should be rounded to the fewest decimal places among the inputs.

Base SI units

The seven fundamental units in the SI system; chemistry focuses on kilogram (mass), meter (length), second (time), mole (amount), and kelvin (temperature).

Kilogram (kg)

Base SI unit of mass.

Meter (m)

Base SI unit of length.

Second (s)

Base SI unit of time.

Mole (mol)

Base SI unit of amount of substance.

Kelvin (K)

Base SI unit of temperature; absolute temperature scale used in science.

Celsius

Temperature scale used in labs; conversion to Kelvin is common (K = C + 273.15).

Prefixes (example set: kilo, centi, milli, micro, nano)

Multipliers added to base units: kilo (10^3), centi (10^-2), milli (10^-3), micro (10^-6), nano (10^-9).

Derived SI units

Units formed by combining base units, such as liter (volume), joule (energy), and density units (e.g., g/mL, kg/m^3).

Liter (L)

Derived SI unit for volume; 1 L = 1000 mL.

Cubic centimeter (cm^3)

Volume unit equal to 1 mL; cm^3 is the same as mL.

Milliliter (mL)

Volume unit equal to one thousandth of a liter; commonly used for liquids.

Gram (g)

Unit of mass; often used in the lab alongside kilograms (1 kg = 1000 g).

Density

Mass per unit volume; common units include g/cm^3 for solids and g/mL for liquids; density can be expressed in various units.

Specific gravity

Dimensionless ratio of a substance’s density to the density of water (approximately 1 g/mL); used to compare density without units.

Volume by length×width×height

Method to calculate volume for regular-shaped solids: V = L × W × H.

Volume by water displacement

Method to determine volume for irregular objects by measuring change in water level in a graduated cylinder (Archimedes principle).

Cubic centimeter equals milliliter

One cubic centimeter (cm^3) is exactly equal to one milliliter (mL); a key equivalence in volume measurements.

Conversion factor

An equality expressed as a fraction used to convert units (e.g., 1 L = 1000 mL); ensures units cancel properly in calculations.

Equality (in units and measurements)

Fixed, exact relationships between quantities (e.g., 60 seconds per minute); used to build conversion factors.

Dimensional analysis

Problem-solving method that uses conversion factors to track units and solve for the desired units.