Chapter 1-7: Chemistry Concepts Review (WuClap, Elements, Properties, and Significant Figures)

Vocabulary flashcards covering the key concepts from the lecture notes, including elements, compounds, mixtures, properties, and significant figures.

Element

A pure substance consisting of only one type of atom; cannot be broken down into simpler substances by chemical means.

Atom

The basic unit of an element; consists of a nucleus of protons and neutrons with orbiting electrons; identity is defined by the number of protons.

Atomic number

The number of protons in the nucleus of an atom; determines the identity of the element.

Proton

A positively charged subatomic particle located in the nucleus; contributes to the element’s identity (via the atomic number).

Neutron

A neutral subatomic particle in the nucleus; contributes to mass but not to charge.

Electron

A negatively charged subatomic particle that orbits the nucleus and largely determines chemical behavior.

Molecule

An assembly of two or more atoms bonded together; can consist of identical or different atoms.

Pure substance

A substance with a definite composition; includes elements and compounds.

Compound

A substance composed of two or more different elements chemically bonded in a fixed ratio.

Mixture

A physical combination of two or more substances that retain their own identities and can be separated by physical means.

Homogeneous mixture

A uniform composition throughout; also called a solution.

Heterogeneous mixture

A nonuniform composition with distinct phases or components.

Solution

A homogeneous mixture formed when a solute is dissolved in a solvent.

Intensive property

A property that does not depend on the amount of substance (e.g., density, temperature).

Extensive property

A property that scales with the amount of substance (e.g., mass, volume).

Density

Mass per unit volume; an intensive property (density = mass/volume).

Mass

The amount of matter in an object; a measure usually in grams or kilograms.

Volume

The amount of space occupied by a substance; measured in liters, milliliters, etc.

Physical property

A property observed without changing the chemical identity of the substance (e.g., color, density, melting point).

Chemical property

A property that describes how a substance undergoes a chemical change or reaction (e.g., flammability).

Physical change

A change that alters form or state but not the chemical identity of a substance (e.g., melting).

Chemical change

A process that changes the chemical identity of a substance (e.g., combustion of glucose).

Exact numbers

Numbers obtained by counting; unlimited precision and do not limit measurement precision.

Inexact numbers

Numbers obtained from measurements; have limited precision based on the measuring device.

Significant figures

Digits that carry meaningful information about precision in a measurement; rules include nonzero digits, zeros between nonzeros, and handling of leading/trailing zeros.

Leading zeros

Zeros at the left of the first nonzero digit; not significant.

Zeros between nonzero digits

Zeros between nonzero digits are significant (e.g., 1005 has four significant figures).

Trailing zeros with decimal

Trailing zeros to the right of a decimal point are significant (e.g., 1.2300 has five significant figures).

Trailing zeros without decimal

Ambiguous; may or may not be significant unless shown in scientific notation or with a decimal point.

Exponential notation (scientific notation)

A number written as a coefficient between 1 and 10 times 10 to an exponent; used to clearly show significant figures.

Multiplication/division significant figures rule

In a calculation, the result should have as many significant figures as the factor with the fewest significant figures.

Addition/subtraction decimal places rule

In a calculation, report the result to the least precise decimal place (least number of decimal places) among the terms.

Exact numbers in calculations

Exact numbers (like counted objects or currency) do not limit the number of significant figures in a result.

Micro- prefix

Prefix meaning 10^-6; used in units like microgram (μg).

One microgram equals

1 μg = 1 x 10^-6 grams.

Currency as exact number

Money amounts like dollars and cents are treated as exact numbers; they are not limited by significant figures.

Accuracy vs. precision

Accuracy: how close a measurement is to the true value; precision: how close repeated measurements are to each other.

Nanogram

A unit of mass equal to $10^{-9}$ grams; denoted as (ng).

mega(M)

10^6 or 1,000,000

Kilo(k)

10³ or 1,000

Deci(d)

10^-1 or 0.1

centi (c

10^-2 or 0.01

mili(m)

10^-3 or 0.001

micro (u)

10^-6 or 0.000001

nano(n)

10^-9 or 0.000000001

pico(p)

10^-12 or 0.000000000001