CHEM 1211 Exam #1 Study Guide - Vocabulary Flashcards

A set of vocabulary flashcards covering essential concepts from Chapter 1 and Chapter 2, including measurements, atomic structure, chemical formulas, the mole concept, and unit conversions.

Nano- (prefix)

A metric prefix meaning 10^-9; used to denote very small quantities such as nanometers.

Nanometer (nm)

A unit of length equal to 1 x 10^-9 meters; commonly used to measure atoms and molecules.

Significant figures (sig figs)

Digits in a measured value that carry meaning about precision, including the last estimated digit.

Addition/subtraction sig figs rule

When adding or subtracting, round the result to the decimal place of the least precise measurement.

Multiplication/division sig figs rule

When multiplying or dividing, round the result to the least number of significant figures among the factors.

Scientific notation

A way of writing very large or small numbers as a product of a decimal and a power of 10 (e.g., 3.2 x 10^4).

Dimensional analysis

A problem-solving method that uses conversion factors to move from one unit to another while preserving equality.

Accuracy

Closeness of a measured value to the true or accepted value.

Precision

Consistency or reproducibility of measurements across trials.

Density

Mass per unit volume of a substance; formula: density = mass / volume.

Density units

Common units include g/mL, g/cm^3, and kg/m^3.

Mass

A measure of the amount of matter in an object (commonly in grams or kilograms).

Volume

The amount of space occupied by a substance (commonly in liters or milliliters).

Atom

The basic unit of an element, containing a nucleus (protons and neutrons) and surrounding electrons.

Molecule

Two or more atoms bonded together forming a discrete unit.

Element

A substance consisting of only one kind of atom.

Compound

A substance composed of two or more elements in a fixed, definite ratio.

Homogeneous mixture

A mixture with uniform composition and properties throughout.

Heterogeneous mixture

A mixture with nonuniform composition, containing distinct phases.

Isotope

Atoms of the same element with the same number of protons but different numbers of neutrons, leading to different mass numbers.

Atomic number (Z)

The number of protons in the nucleus; identifies the element.

Mass number (A)

The total number of protons and neutrons in the nucleus.

Proton

Positively charged subatomic particle in the nucleus; contributes to atomic number.

Neutron

Electrically neutral subatomic particle in the nucleus; contributes to mass.

Electron

Negatively charged subatomic particle orbiting the nucleus; much smaller mass than protons or neutrons.

Neutral atom

An atom with equal numbers of protons and electrons; no net charge.

Cation

A positively charged ion formed when an atom loses electrons.

Anion

A negatively charged ion formed when an atom gains electrons.

Molecular formula

The actual number and type of atoms in a molecule (e.g., H2O).

Empirical formula

The simplest whole-number ratio of atoms in a compound.

Structural (constitutional) isomers

Compounds with the same molecular formula but different connectivity/order of atoms.

Mole concept

A unit for amount of substance; 1 mole contains 6.022 x 10^23 entities.

Avogadro's number

6.022 x 10^23 entities per mole—used to convert between moles and number of particles.

Molar mass

Mass per mole of a substance, expressed in g/mol; sum of atomic masses in the formula.

Grams to moles

Moles = mass (g) / molar mass (g/mol).

Moles to molecules

Molecules = moles x Avogadro's number (6.022 x 10^23).

Celsius to Kelvin

K = C + 273.15.

Fahrenheit to Celsius

C = (F − 32) × 5/9.

Percent composition

The mass percent of each element in a compound.