Chapter 1: Significant figures, dimensional analysis, and atomic theory history

Vocabulary flashcards covering key concepts from the lecture notes on significant figures, dimensional analysis, units, and the history of atomic theory and the periodic table.

Significant figures

Digits in a measured value that reflect its precision and determine how many digits should be kept in calculations.

Addition and subtraction with significant figures

When adding or subtracting, align decimals; the result has the same last significant figure as the least precise decimal place among the inputs.

Multiplication and division with significant figures

The result has as many significant figures as the operand with the fewest significant figures.

Last significant figure

The rightmost digit that is considered significant in a measurement; it marks the limit of precision.

Precision

The degree to which repeated measurements under unchanged conditions yield similar results; relates to how many digits are known.

Dimensional analysis

A method that uses units as algebraic factors to check calculations and convert quantities to the same units.

Unit

A standard quantity used to express a measurement; when adding or subtracting, units must match; operations produce units according to the operation.

Conservation of mass

In chemical reactions, the total mass of reactants equals the total mass of products.

Volume by displacement

Determining the volume of an object by measuring the change in liquid volume when the object is submerged.

Element

A substance that cannot be decomposed into simpler substances by chemical means.

Compound

A substance made of two or more elements in fixed small whole-number mass ratios.

Atom

The basic unit of an element that retains the properties of that element.

Molecule

A group of two or more atoms bonded together, forming a discrete unit.

Dalton

Early chemist who proposed atoms combine in simple whole-number ratios and that mass is conserved in reactions.

Berzelius

Chemist who introduced standardized chemical symbols and helped establish mass relationships for elements.

Avogadro

Hypothesized that equal volumes of gases contain the same number of particles, leading to Avogadro’s number and the idea that elements are made of atoms or molecules.

Mendeleev

Creator of the periodic table; arranged elements by chemical behavior and mass and predicted undiscovered elements.

Periodic table

A table organizing elements into columns with similar chemistry; arranged by atomic number and groups of similar properties.

Atomic number

The number of protons in an atom’s nucleus; identifies the element and orders the periodic table (discovered by Moseley).

Atomic mass

Mass of an atom, traditionally expressed in atomic mass units; related to the masses of protons and neutrons and used to compare substances.

X-ray emission (Moseley’s work)

Relation between X-ray energies and atomic numbers; provided a physical basis for the periodic table.

Hydrogen

The lightest element; historically used as a reference in atomic mass ideas; often exists as H2 in nature.

Density

Mass per unit volume; used as an example of applying significant figures and dimensional analysis in calculations.

Law of definite proportions

In compounds, elements combine in fixed, simple whole-number mass ratios.