Chemistry: The Central Science - Key Vocabulary

Vocabulary flashcards covering key concepts, terms, and definitions from the notes on chemistry, matter, measurement, and atomic theory.

Chemistry

The study of the composition, properties, and interactions of matter; called the central science because it connects to biology, physics, medicine, and environmental science.

Central Science

A nickname for chemistry highlighting its connections to many other STEM fields.

Scientific Method

The process to learn about the natural world through observation and experimentation, typically involving observation/question, hypothesis, experimentation, and conclusion.

Observation

Noticing and asking questions about a phenomenon before forming a hypothesis.

Hypothesis

A tentative, testable explanation or educated guess about an observation.

Experimentation

Conducting controlled tests to verify or disprove a hypothesis.

Conclusion

Assessment of results from experiments; if well supported, a hypothesis may contribute to a theory.

Theory

A well-substantiated explanation for a broad aspect of nature (e.g., Atomic Theory).

Law

A concise statement describing what happens in nature, often based on extensive observations; it does not necessarily explain why.

Macroscopic Domain

The realm of matter visible to the naked eye; everyday observations (e.g., a glass of water).

Microscopic Domain

The realm of atoms, molecules, and ions too small to see; often requires imagination or models.

Symbolic Domain

The language of chemistry using symbols, formulas, and equations to represent macroscopic and microscopic phenomena.

Element

A pure substance consisting of only one type of atom that cannot be broken down by chemical means.

Compound

A pure substance made of two or more elements chemically bonded in a fixed ratio.

Pure Substance

Matter with a constant composition and distinct properties (elements or compounds).

Mixture

A combination of two or more substances not chemically bonded.

Homogeneous Mixture

A mixture with uniform composition throughout (a solution).

Heterogeneous Mixture

A mixture with non-uniform composition; parts are visibly different.

Atom

The smallest unit of an element; the basic unit of matter.

Molecule

Two or more atoms bonded together.

Physical Property

A characteristic observed without changing the substance’s chemical identity (e.g., color, density).

Physical Change

A change in state or appearance without changing the chemical identity (e.g., melting, dissolving).

Chemical Property

The ability of a substance to undergo a chemical change (e.g., flammability, acidity).

Chemical Change

A process that produces one or more new substances (e.g., rusting, burning).

Extensive Property

Property that depends on the amount of matter (e.g., mass, volume).

Intensive Property

Property that does not depend on amount of matter (e.g., density, temperature, color).

Mass

A measure of the amount of matter in an object; constant regardless of location.

Weight

The gravitational force on an object’s mass; varies with location (e.g., Earth vs Moon).

State of Matter

Solid, liquid, gas, or plasma.

Solid

Definite shape and definite volume.

Liquid

Definite volume but takes the shape of its container.

Gas

Fills both the shape and volume of its container.

Plasma

A high-energy, ionized gas with charged particles (found in stars, lightning).

Volume

The amount of space an object occupies; SI unit is cubic meter (m³); common units are liter (L) and milliliter (mL); 1 mL = 1 cm³.

Density

Mass per unit volume; an intensive property; common units: g/cm³ (solids/liquids) or g/L (gases).

Uncertainty

Doubt in a measurement; exact numbers have no uncertainty; measured numbers have uncertainty.

Exact Numbers

Values that are counted or defined precisely with no uncertainty (e.g., 12 eggs, 100 cm).

Uncertain Numbers

Numbers obtained from measurements and inherently carry uncertainty.

Accuracy

How close a measurement is to the true or accepted value.

Precision

How close a set of measurements are to each other.

Significant Figures

All certain digits plus one uncertain digit; rules determine which digits are significant.

Dimensional Analysis

Problem-solving method using conversion factors to change units.

Conversion Factor

A ratio of two equivalent quantities used to convert units (e.g., 1 in = 2.54 cm).

1 mL = 1 cm³

Volume equivalence used to convert between liters/milliliters and cubic centimeters.

Celsius

Temperature scale; Kelvin = Celsius + 273.15; used with metric system.

Kelvin

SI base temperature scale; 0 K = absolute zero.

Fahrenheit

Temperature scale used in some regions; formulae convert to/from Celsius and Kelvin.

Temperature Conversions

Formulas to convert between Celsius, Kelvin, and Fahrenheit (e.g., K = C + 273.15; F = (9/5)C + 32; C = (5/9)(F − 32)).

Dalton's Atomic Theory

Five postulates: matter is composed of atoms; elements are made of identical atoms; atoms differ between elements; compounds form from atoms in simple whole-number ratios; atoms are rearranged, not created/destroyed in reactions.

Law of Conservation of Matter

Matter is conserved in chemical reactions because atoms are merely rearranged.

Law of Definite Proportions

A pure compound always contains the same elements in the same proportion by mass.

Law of Multiple Proportions

If two elements form more than one compound, the masses of the second element in a fixed mass of the first are in small whole-number ratios.