Chemistry Lecture Notes: Density, Energy, and Atomic Concepts (Chapter E and Chapter One)

Vocabulary flashcards covering key concepts from density, measurement, energy, thermodynamics, and basic matter classifications discussed in the lecture notes.

Density

Mass per unit volume; D = m/V; commonly reported in g/cm^3 or kg/L.

Volume

Amount of space occupied by a substance; for a cube, volume = side^3; SI unit m^3 (cm^3 in the notes).

Mass

Amount of matter; measured in grams or kilograms.

Significant figures (sig figs)

Rules for reporting precision; in multiplication/division, the result has the same number of sig figs as the factor with the fewest sig figs.

Exact conversions (inch to cm)

1 inch = 2.54 cm (exact, does not limit precision).

Exact conversions (kg to g)

1 kilogram = 1000 grams (exact, does not limit precision).

Density problem setup

Use D = m/V; convert mass to grams and volume to cubic centimeters to obtain density in g/cm^3.

Internal energy (U)

Total energy of a system; sum of kinetic and potential energy components.

Kinetic energy

Energy of motion; KE = 1/2 m v^2; includes translation, rotation, and vibration in molecules.

Potential energy

Energy associated with position; includes chemical energy from bonds.

Heat

Form of energy transferred between objects due to a temperature difference; symbol Q; flows from hot to cold.

Temperature

Measure of the average kinetic energy of particles; not the energy itself.

First Law of Thermodynamics

ΔU = Q + W; energy is conserved; change in internal energy equals heat added plus work done.

Joule

SI unit of energy; 1 J = 1 kg·m^2·s^-2.

Calorie (lowercase c)

Energy to raise 1 g of water by 1°C; approximately 4 J.

Calorie (uppercase C) / kilocalorie

Food calorie; 1 Cal = 1000 cal ≈ 4,000 J (4 kJ).

Watt

Unit of power; 1 W = 1 J/s.

Kilowatt-hour (kWh)

Energy equal to 1000 W for 1 hour; 1 kWh ≈ 3.6 × 10^6 J.

Elements

Pure substance composed of one type of atom; found on the periodic table.

Compounds

Pure substance composed of two or more elements chemically bonded; has a chemical formula.

Mixtures

Combination of substances not chemically bonded; can be homogeneous or heterogeneous.

Homogeneous mixture

Uniform composition; components not easily distinguishable (e.g., salt in water).

Heterogeneous mixture

Nonuniform composition; components are distinguishable (e.g., muddy water).