Properties and States of Matter

Properties of Matter

• Substances are described by properties, classified as physical or chemical.
• Physical properties can be observed without changing the substance's identity (e.g., color, hardness, conductivity, density); physical changes are reversible.
• Physical properties can be intensive (independent of quantity, e.g., odor) or extensive (dependent on quantity, e.g., volume).
• Chemical properties describe how a substance reacts with others (e.g., tendency to combine, color change, heat emission).

States of Matter

• Matter exists as solids, liquids, and gases.

• Solids have fixed shape and volume, with tightly packed atoms vibrating in place.

• Liquids have definite volume but indefinite shape, with loosely bonded atoms.

• Gases have neither definite shape nor volume, with widely spaced, rapidly moving atoms; gases are compressible.

• Phase changes are transitions between states (e.g., melting, freezing, vaporization, condensation).

• Melting is a temperature increase leading to a phase change.

• Freezing occurs when a liquid's temperature drops to become a solid

• Vaporization is the addition of energy to cause a phase change into a gas.

• Condensation is when water vapor cools and becomes a liquid.

• Both physical and chemical changes can occur in matter transitioning between states.

• The Law of Conservation of Matter applies to these changes.

Atomic Structure

• Atoms are the fundamental units of matter.
• Atoms consist of a nucleus (protons and neutrons) and an electron cloud (electrons).
• Protons are positively charged, neutrons are neutral, and electrons are negatively charged.
• Atoms are too small to be observed directly, studied via models.
• Elements are different types of atoms, each with unique properties.
• The Big Bang resulted in the creation of atoms.

Elements and the Periodic Table

• Elements are pure substances composed of a single type of atom.
• Different elements have different numbers of protons, which defines their identity.
• The Periodic Table organizes elements based on their properties.
• Each element has an atomic number (equal to the number of protons).

Isotopes

• Isotopes are atoms of the same element with different numbers of neutrons.
• Isotopes share the same chemical properties.
• Isotopes have different physical properties.
• Isotopes can be stable or radioactive (unstable).
• Isotopic abundance refers to the percent of each isotope's presence in nature.
• Radioactive decay follows a measurable pattern quantified by half-life.

Ions

• Ions form when atoms gain or lose electrons.
• Positively charged ions are cations.
• Negatively charged ions are anions.
• Ions can be single atoms, molecules, or compounds.
• Monoatomic ions consist of a single atom.
• Polyatomic ions have multiple atoms bonded together with a net charge.
• Noble gases do not typically form ions due to their stable electron configurations that prevent bonds from forming.

Types of Bonds

• Ionic bonds form between metals (cations) and nonmetals (anions) with the transfer of electrons creating ions with opposing charges that are attracted to each other.
• Covalent bonds form between nonmetals when atoms share electrons.
• Nonpolar covalent bonds occur when electrons are shared equally.
• Polar covalent bonds occur when electrons are shared unequally.
• Metallic bonds involve a "sea" of electrons shared among metal atoms.
• Hydrogen bonds occur between hydrogen atoms and other electronegative atoms.

Classification of Matter

• Matter can be classified as mixtures or pure substances.

• Mixtures are combinations of two or more substances.

• Pure substances are either elements, compounds, or molecules.

• Elements are made of only one type of atom.

• Compounds are made of two or more elements bonded together in a fixed ratio.

• Molecules are groups of atoms bonded together.

• Ionic compounds are formed from ionic bonds.

• Covalent compounds are formed from covalent bonds.