Chem 2026 — Chapter 1

What is chemistry?

The study of matter and behavior of atoms and molecules

What is matter?

Anything that has mass and occupies space

What is an atom?

A tiny block of matter

What is a molecule?

Two or more atoms chemically combined

What does structure deternine?

Structure helps determine a substance’s properties

What is an observation?

A statement or measurement describing what is seen

What is a hypothesis?

A testable explanation for observations

What is a scientific law?

A summary of what happens in nature

What is a scientific theory?

An explanation of why something happens in nature

Element vs compound?

An element has one kind of atom: a compound has two or more elements chemically bonded

Pure substance vs mixture?

A pure substance has one chemical substance only; a mixture contains two or more substances physically combined

Physical property?

A property observed without changing identity (eg. density or melting point)

Chemical property?

A property describing the ability to form a new substance (eg. flammibility)

What is chemical energy?

A form of potential energy stored in substances

What is the SI unit of temperature?

Kelvin (K)

Celsius to Kelvin?

K = C + 273.15

Celsius to Fahrenheit?

F = (9/5)(C) +32

Fahrenheit to Celsius?

C = (F-32) x 5/9

What is density?

Mass divided by volume

Density formula?

d = m/V

Mass from density?

m = d x V

Volume from density?

V = m/d

What is an extensive property?

A property that depends on the amount of substance (eg. mass and volume)

What is an intensive property?

A property that does not depend on the amount of a substance (eg. density, color, melting point)

What are significant figures?

Digits that show the precision of a measurement

Exact numbers have how many sig figs?

Unlimited

Multiplication/division sig fig rule?

Answer has the same # of sig figs as the factor with the fewest sig figs

Addition/subtraction sig fig rule?

Answer has the same # of decimal places as the term with the fewest decimal places

What is precision?

How close repeated measurements are to each other

What is accuracy?

How close a measurement is to the true value

Best order for solving chem math problems?

Write formula, substitue numbers with units, solve, then round