Chem 119 so far

Chemistry

The study of matter and the changes it undergoes.

Atoms-first approach

An approach to chemistry based on understanding atoms to explain macroscopic structures, molecule formation, attraction between molecules, and chemical behavior.

Angstrom (Å)

A unit of length used on the atomic scale. 1 Å = 1 × 10^-10 meters.

Nanometer (nm)

A unit of length equal to 10 Å.

Scanning Tunneling Microscopy (STM)

A technique used to visualize atoms.

Atomic Force Microscopy (AFM)

A technique used to visualize matter at the molecular and atomic scale.

Femtosecond (fs)

A unit of time equal to 1 × 10^-15 seconds.

Homogeneous mixture

A mixture consisting of two or more substances in the same phase with uniform composition.

Heterogeneous mixture

A mixture that does not have uniform composition and whose components are visually distinguishable.

Pure substance

A substance with well-defined physical and chemical properties.

Types of pure substances

Elements and compounds.

Element

A pure substance consisting of only one type of atom that cannot be decomposed or further simplified by ordinary means.

Compound

A substance composed of two or more elements.

Molecule

The smallest unit of a compound that retains the chemical characteristics of the compound.

Chemical formula

A representation showing the types and numbers of atoms in a compound.

Water

H2O.

Ethanol

CH3CH2OH.

Caffeine

C8H10N4O2.

Density

A physical property that can be used to separate substances by decantation or centrifugation.

Boiling point

A physical property that can be used to separate substances through distillation.

State of matter

A physical property that can be used to separate substances through filtration.

Intermolecular forces

A physical property that can be used to separate substances through chromatography.

Vapor pressure

A physical property that can be used to separate substances through evaporation.

Magnetism

A physical property that can be used to separate substances using magnets.

Solubility

A physical property that can be used to separate substances through filtration.

Extensive property

A property that depends on the amount of material present.

Examples of extensive properties

Mass and volume.

Intensive property

A property that is independent of the amount of material present.

Examples of intensive properties

Melting point, boiling point, and density.

Scientific method

A framework for gaining and organizing knowledge and a procedure for processing and understanding scientific information.

Observation

A witnessed phenomenon that can be recorded.

Interpretation

A possible explanation of the reason behind a phenomenon.

Theory (model)

A set of tested hypotheses that gives an overall explanation of a natural phenomenon.

Natural law

An observation that applies to many different systems.

Law vs. theory

A law states how a particular phenomenon occurs, while a theory attempts to explain why the phenomenon occurs.

Law of Conservation of Matter

There is no observable change in the quantity of matter during a chemical reaction or physical change.

Law of Conservation of Mass

Mass is neither created nor destroyed.

Law of Conservation of Energy

Energy cannot be created or destroyed in a chemical reaction or physical change; it can only be converted from one form to another.

Ex nihilo nihil fit

"Out of nothing comes nothing."

Ancient Greek view of matter

The belief that all matter was composed of earth, air, fire, and water.

Alchemy

A practice prevalent for about 2,000 years during which several elements were discovered and methods for preparing mineral acids were developed.

Robert Boyle

Considered the first "chemist" in the lecture; he introduced quantitative physics and chemistry and quantified the relationship between pressure and air.

Boyle's view of elements

Elements cannot be further broken down.

Georg Stahl

Scientist who suggested the existence of phlogiston.

Phlogiston

A historical and incorrect concept proposed by Georg Stahl.

Joseph Priestley

Scientist who discovered the existence of oxygen.

Antoine Lavoisier and Marie-Anne Paulze Lavoisier

Associated with the Law of Conservation of Mass.

Law of Definite Proportion

A given compound always contains exactly the same proportion of elements by mass.

Joseph Proust

Scientist associated with the Law of Definite Proportion.

Law of Multiple Proportions

When two elements form a series of compounds, the ratios of the masses of the second element that combine with 1 gram of the first element can always be reduced to small whole numbers.

John Dalton

Scientist associated with the Law of Multiple Proportions and Dalton's Atomic Theory.

Dalton's Atomic Theory

Atomic theory proposed in 1808 describing the nature of atoms, elements, compounds, and chemical reactions.

Dalton's Atomic Theory — Elements

Each element is made up of tiny particles called atoms.

Dalton's Atomic Theory — Same element

The atoms of a given element are identical.

Dalton's Atomic Theory — Different elements

The atoms of different elements are different in some fundamental way or ways.

Dalton's Atomic Theory — Compounds

Chemical compounds form when atoms of different elements combine with each other.

Dalton's Atomic Theory — Compound composition

A given compound always has the same relative numbers and types of atoms.

Dalton's Atomic Theory — Chemical reactions

Chemical reactions involve the reorganization of atoms and changes in how they are bound together.

Atoms during chemical reactions

According to Dalton, atoms themselves are not changed during a chemical reaction.

Dalton's atomic masses

Dalton prepared the first table of atomic masses, also called atomic weights.

Problem with Dalton's atomic masses

Most were inaccurate because of incorrect assumptions about the formulas of certain compounds.

Joseph Gay-Lussac

Scientist who measured the volumes of gases reacting with each other under identical conditions of temperature and pressure.

Avogadro's hypothesis

At the same temperature and pressure, equal volumes of different gases contain the same number of particles.

Condition for Avogadro's hypothesis

The gases are compared at the same temperature and pressure.