Chem121K, Lecture 1

Vocabulary flashcards covering key concepts from the notes on substances, energy, amount of substance, measurement concepts, and data quality.

Mixture

A substance that is not a pure substance; composed of two or more substances physically combined.

Pure substance

A substance with a uniform composition that is either a single element or a single compound.

Allotrope

Different structural forms of the same element (e.g., diamond and graphite are allotropes of carbon).

Diamond

An allotrope of carbon.

Graphite

An allotrope of carbon.

States of matter

Distinct forms of matter: solid, liquid, and gas.

Solid

A state of matter in which molecules are closely packed, giving a definite shape and volume.

Liquid

A state of matter with molecules less tightly packed than a solid; definite volume but adaptable shape.

Gas

A state of matter in which molecules are far apart and fill the space available.

SI base units

The fundamental units in the SI system used to measure physical quantities: meter (length), second (time), mole (amount of substance), and ampere (electric current).

Meter

The SI base unit of length.

Second

The SI base unit of time.

Mole

The SI base unit for amount of substance; number of particles (6.022×10^23 per mole).

Ampere

The SI base unit of electric current.

Standard

A reference material with a known value used to calibrate instruments and assess accuracy.

Accuracy

Closeness of a measured value to the true value.

Precision

Closeness of repeated measurements to each other.

True value

The actual value that measurements aim to approximate.

Significant figures

Digits in a number that carry meaning about precision; rules determine which zeros are significant.

Concentration

Amount of solute per unit volume in a solution; used to describe how much is present.

Calibration

Process of adjusting an instrument to produce accurate results by comparing with a standard.

Unit conversion

Process of converting quantities from one unit to another using conversion factors.