Foundations of Chemistry and Physics Concepts

Understanding Physical Sciences

Branches of Physical Science

• Chemistry: The study of the composition, structure, and properties of substances. It is the science that investigates the composition, structure, and properties of matter.
• Physics: The science that deals with matter, energy, motion, and force.
• Earth Science: The study of Earth and its various components.

Why Chemistry is a Physical Science

Chemistry is considered a physical science because it studies what exists around the world, such as atoms and molecules. Physical sciences primarily focus on non-living things.

Fundamental Concepts of Matter

Basic Definitions

• Mass: A measure of the amount of matter in an object.
• Matter: Anything that has mass and takes up space.
• Atom: The smallest unit of an element that retains the chemical identity of that element.
• Element: A pure substance that cannot be separated or broken down into simpler substances by chemical means. Elements are made up of atoms.
• Compound: A substance made up of two or more different elements chemically bonded together. Compounds can be broken down into simpler substances by chemical means.

States of Matter

• Liquid: A state of matter that has a definite volume but not a definite shape; it takes the shape of its container.
• Gas: A state of matter that has neither a definite volume nor a definite shape; it expands to fill its container.
• Plasma: A high-temperature state of matter in which atoms lose most of their electrons, forming an ionized gas.

Chemical Changes and Reactions

Key Terms in Chemical Processes

• Chemical Property: A characteristic or behavior of a substance that can be observed when it undergoes a chemical change or reaction.
• Chemical Change: A change that occurs when one or more substances are transformed into new and different substances.
• Chemical Reaction: A process that involves the rearrangement of the molecular or ionic structure of a substance, as opposed to a change in physical form or a nuclear reaction. It is a chemical change that forms new substances.
• Reactant: A substance or molecule that participates in a chemical reaction.
• Product: A substance that forms as a result of a chemical reaction.

Mixtures and Pure Substances

Understanding Combinations of Matter

• Mixture: A combination of two or more substances that are not chemically combined.
• Homogeneous Mixture (Solution): A mixture in which the components are uniformly distributed throughout and appear as a single phase. Solutions are homogeneous mixtures of two or more substances.
• Heterogeneous Mixture: A mixture in which the components are not uniformly distributed and can be easily distinguished from one another. Unlike homogeneous mixtures, the components of heterogeneous mixtures do not mix together uniformly.
• Pure Substance: A substance that always has a fixed composition and uniform properties throughout. Pure substances can be either elements or compounds.

The Scientific Method

Steps of Scientific Inquiry

1. Observing: Noticing phenomena or events.
2. Asking a Question: Formulating a question based on observations (e.g., "Why does that occur in my experiment?").
3. Forming a Hypothesis: Proposing a testable explanation for the observation, often involving research to answer the question.
4. Making a Prediction: Stating an expected outcome based on the hypothesis (e.g., "If my hypothesis is correct, then...").
5. Testing the Prediction: Conducting experiments or observations to see if the prediction is supported or contradicted (e.g., "Try my experiment again").
6. Iterating: Reflecting on the results and refining the hypothesis or experiment as needed.

Periodic Table and Material Properties

Periodic Table Organization

• Group: A vertical column in the periodic table, containing elements with similar chemical properties.
• Period: A horizontal row in the periodic table, representing elements with the same number of electron shells.

Classification of Elements

• Metal: Typically good electrical and heat conductors, malleable, and ductile.
• Metalloid: Elements that share characteristics of both metals and nonmetals.
• Nonmetal: Generally poor heat and electrical conductors, often brittle.

Proportional Relationships

Understanding Variable Relationships

• Directly Proportional: A relationship between two variables where their ratio is equal to a constant value. As one variable increases, the other increases proportionally.
• Inversely Proportional: A relationship between two variables where their product is equal to a constant value. As one variable increases, the other decreases proportionally.

Pioneers in Atomic Theory

Key Discoveries in Atomic Structure

• J.J. Thomson: Through his cathode ray experiment, Thomson provided evidence that atoms contain negatively charged particles, which were later called electrons.
• Ernest Rutherford: Discovered the atomic nucleus and concluded that it was significantly smaller compared to the total volume of an atom.

Atomic Structure and Moles

Atomic Characteristics

• Atomic Number: The amount of protons found in the nucleus of an atom. It defines the element.
• Isotope: Atoms of the same element that have different masses due to a different number of neutrons.
• Mass Number: The total number of protons and neutrons in an atom's nucleus.
• Average Atomic Mass: The weighted average mass of the isotopes of an element, expressed in atomic mass units (amu).

The Mole Concept

• Mole (mol): A unit of measurement used to express amounts of a chemical substance. It is defined as the number of atoms of that element equal to the number of atoms in exactly 12 grams of carbon-12.
• Avogadro's Number: The number of particles (atoms, molecules, ions, etc.) in one mole of a pure substance, approximately 6.022 x 10²³.
• Molar Mass: The mass of one mole of a pure substance, typically expressed in grams per mole (g/mol).

Fundamental Laws of Chemistry

Guiding Principles of Chemical Reactions

• Law of Conservation of Mass: States that matter cannot be created or destroyed during a chemical or physical change. The total mass of reactants equals the total mass of products.
• Law of Definite Proportions: States that a chemical compound always contains the same elements in exactly the same proportions by mass, regardless of the size of the sample or source.
• Law of Multiple Proportions: States that when two elements combine to form two or more different compounds, the ratio of the masses of one element that combine with a fixed mass of the other element can be expressed as a ratio of small whole numbers.

Isotopes: Similarities and Differences

Distinguishing Isotopic Forms

• Differences: Isotopes of a particular element are different because they have a different number of neutrons, leading to different masses.
• Similarities: They are alike because they have the same number of protons, which means they are the same element and have the same atomic number.

Chemical Calculations

Essential Formulas and Conversions

• Calculating Average Atomic Mass: Multiply the atomic mass of each isotope by its percent abundance (as a decimal), then add the results and round to an appropriate number of significant figures.
• Moles to Grams Conversion: To convert moles to grams, multiply the number of moles by the molar mass of the substance.
• Grams to Moles Conversion: To convert grams to moles, divide the mass in grams by the molar mass of the substance.

Electron Configuration Basics

Electron Shells and Sublevels

Electron energy levels hold sublevels, which have specific capacities for electrons:

• s-sublevel: holds up to 2 electrons
• p-sublevel: holds up to 6 electrons
• d-sublevel: holds up to 10 electrons
• f-sublevel: holds up to 14 electrons