Introduction to Chemistry and Physics: Key Concepts and Definitions

Chemistry and Physics Basics

Chemistry

The study of the composition, structure, and properties of matter.

Physics

The study of the principles of matter and energy.

Earth Science

The study of Earth and its neighbors in space.

Matter and Its Properties

Mass

A measure of the amount of matter.

Matter

Anything that has mass and takes up space.

Atom

The smallest unit of an element.

Element

A pure substance that cannot be broken down into simpler substances, made up of atoms.

Compound

Made up of elements and can be broken down into simpler substances.

States of Matter

• Liquid: A state of matter that has a definite volume but not a definite shape.
• Gas: A state of matter with no definite volume or shape.
• Plasma: A high-temperature state of matter in which atoms lose most of their electrons.
• Solid: A state of matter with a definite volume and shape.

Chemical Properties and Changes

Chemical Property: A substance's ability to undergo changes that transform it into a different substance.

Chemical Change: A change in the chemical composition of elements where one substance turns into another.

Chemical Reaction: Rearranges the constituent reactants and involves the rearrangement of the ionic or molecular structure of a substance.

Reactant: Substances that react in a chemical change.

Product: Substances formed by a chemical change.

Mixtures

Mixture: A blend of two or more kinds of matter, each of which maintains its identity and properties.

Homogeneous Mixture: A mixture where the components are uniformly distributed throughout.

Solution: A homogeneous mixture of two or more substances uniformly dispersed throughout a single phase.

Heterogeneous Mixture: A mixture that does not mix fully.

Pure Substance: Always homogeneous, with a fixed composition; can be an element or a compound.

Atomic Structure and Isotopes

Atomic Number

The number of protons in the nucleus of an atom, which defines an element.

Isotope

Atoms of the same element that have different numbers of neutrons, and therefore different masses.

Mass Number

The total number of protons and neutrons in the nucleus of an isotope.

Average Atomic Mass

The weighted average of the atomic masses of the naturally occurring isotopes of an element.

Moles and Molar Mass

Mole

The amount of a substance that contains as many particles as there are atoms in 12 grams of carbon-12 (Avogadro's number).

Avogadro's Number

The number of particles in exactly one mole of a pure substance (6.022 x 10²³).

Molar Mass

The mass of one mole of a pure substance.

The Periodic Table

Organization

• Group: Vertical columns on the periodic table.
• Period: Horizontal rows on the periodic table.

Types of Elements

• Metal: A good conductor of heat and electricity.
• Metalloid: An element that shares properties of both metals and nonmetals.
• Nonmetal: A poor conductor of heat and electricity.

Relationships Between Variables

Direct Proportion

A relationship between two variables where their ratio is constant.

Inverse Proportion

A relationship between two variables where their product is constant.

Isotopes: Similarities and Differences

Similarities

Isotopes of the same element have the same number of protons.

Differences

Isotopes of the same element have different numbers of neutrons.

Calculations

Moles to Grams

• To convert moles to grams, multiply by the molar mass.
• To convert grams to moles, divide by the molar mass.

Extensive and Intensive Properties

Extensive Property

A property that depends on the amount of matter in a sample (e.g., mass, volume, weight).

Intensive Property

A property that does not depend on the amount of matter in a sample (e.g., density, color, temperature).

Electron Configuration

Levels hold sublevels, which are:

• s: 1 orbital, holds up to 2 electrons
• p: 3 orbitals, holds up to 6 electrons
• d: 5 orbitals, holds up to 10 electrons
• f: 7 orbitals, holds up to 14 electrons