Key Terms
Chemistry
The study of the composition, properties, and interactions of matter.
Hypothesis
A tentative explanation of observations; guides data collection; tested by experiment.
Law
Summarizes a large body of experimental observations; describes or predicts what happens in nature. Does not explain why
Theory
A well-substantiated, comprehensive, testable explanation of why something happens. Supported by a large body of evidenc
Macroscopic
Things large enough to see and touch directly -- liquids, solids, gases, color, temperature, density. What you observe i
Microscopic
Atoms, molecules, ions, electrons, chemical bonds. Too small to see; understood through inference and imaging tools.
Symbolic
The language chemists use to represent both domains -- chemical formulas (H2O), symbols (O, Na), equations, graphs, and
Matter
Anything that occupies space and has mass.
Solid
Rigid, definite shape, definite volume. Liquid: definite volume, takes the shape of its container; forms a flat surface
Gas
Takes both the shape and volume of its container. Plasma: a fourth state; high-energy gas with electrically charged part
Mass
The amount of matter in an object. Does not change based on location.
Atom
Smallest unit of an element retaining that element's properties.
Molecule
Two or more atoms joined by chemical bonds; moves as a unit.
Compounds exist as molecules of different atoms
Water (H2O), carbon dioxide (CO2), glucose (C6H12O6).
Physical property
Characteristic observed without changing the substance's chemical identity. Examples: density, color, hardness, melting