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Introduction to Matter - Comprehensive Study Notes

Matter and Atoms

  • Matter is anything that has mass and occupies space.
  • Atoms are the smallest particles of an element that can exist and still contain the properties of the original element.
  • Atoms are too small to see with the naked eye.
    • Size estimated at 4\times 10^{-9}\ \text{inches} (four-billionths of an inch).
    • Electron microscopes photograph atom-like features; magnification factors can reach the millions.
  • Mass vs Weight:
    • Mass = amount of matter in a body (unit: grams).
    • Weight = Earth's gravitational attraction on a body (unit: pounds).

Physical States of Matter

  • Solid
    • Has a definite shape and does not have to conform to the container shape.
    • Particles (atoms/ions) adhere rigidly.
    • Two types of solids:
    • Crystal: Regular repeating units, long-range order, very ordered particle arrangement (e.g., salt, sugar).
      • \text{Crystal: long-range order}
    • Amorphous: Irregular units, no long-range order (e.g., plastic, glass, gels).
      • \text{Amorphous: no long-range order}
  • Liquid
    • Definite volume.
    • Particles slide past one another; not rigidly adhered.
    • No definite shape; takes the shape of its container.
  • Gas
    • Indefinite shape and volume; completely fills its container.
    • Takes the shape and volume of its container.
    • Particles move independently of one another.
  • Plasma (a state of matter)
    • Very hot ionized gas.
    • Contains light and photons; charged particles (electrons, positive ions, some negative ions).
    • Examples: the Sun is plasma; surface temperature around 6\times 10^{3}^\circ\text{C}; fusion reactions release large amounts of energy; lightning is plasma.
  • Quick recall from Learning Check:
    • Unknown matter that moves independently, carries no charge, may be colored or colorless, and fills a room is a gas.
    • Learning Check Solution highlights:
    • Gas vs liquid: gas particles move independently; liquid particles slide past one another.
    • Plasma vs gas: plasma carries a charge; gas does not.
    • Color: Bromine gas is colored; oxygen gas is colorless.
    • Both gases and plasmas fill containers; answer to the learning check: gas.

Substances and Mixtures

  • Substance
    • A particular type of matter with fixed composition (pure) and one phase.
  • Mixture
    • Contains two or more substances with variable composition.
    • May have more than one phase.
  • Phase
    • A homogeneous part of a system separated from other parts by a physical boundary.
  • Substances vs Mixtures examples
    • Elements: Cu (copper) and F (fluorine) can be separated into their elemental forms.
    • Compounds: chemically combined substances with fixed composition; e.g., copper(II) fluoride (CuF2).
    • Ionic compound: decomposes only by chemical means; e.g., \text{H}_2\text{O} (water) is a covalent compound; but an ionic compound example is \text{NaCl}.
    • Covalent molecules: composed of atoms bonded by covalent bonds; e.g., \text{H}2\text{O}, \text{H}2\text{O}_2.
  • Diatomic molecules
    • Elements that exist as two-atom molecules: \mathrm{H2},\ \mathrm{O2},\ \mathrm{N2},\ \mathrm{Cl2},\ \mathrm{Br2},\ \mathrm{I2},\ \mathrm{F_2}.
    • Mnemonic (HONClBrIF) to remember diatomic elements: Have No Fear Of Ice Cold Beer.
  • Mixtures: homogeneous vs heterogeneous
    • Homogeneous: single phase, uniform throughout (e.g., \text{NaCl} + \text{H}_2\text{O}; sugar + water).
    • Heterogeneous: two or more phases (e.g., sand + water; oil + vinegar).
  • Learning Check: Classification examples
    • Sand: heterogeneous mixture.
    • Ice ((\mathrm{H_2O})): compound and molecule (water).
    • Flour: typically a pure substance (often considered a component of a mixture depending on context).
    • Table Salt ((\mathrm{NaCl})): compound.

Properties of Substances

  • Physical property
    • Can be observed or measured without changing the substance's identity/composition.
    • Examples: color, odor, physical state (s, l, g), melting point, boiling point, density, magnetism, etc.
  • Chemical property
    • Describes the ability to form a new substance.
    • Example: iron can rust (oxidize); gold does not rust under typical conditions.
  • Reversibility of processes
    • Physical changes are typically reversible (e.g., freezing/melting, evaporation/condensation).
    • Chemical changes are generally not easily reversible (e.g., rust formation). In many cases, physical changes are reversible; chemical changes are not.

Changes in Matter

  • Physical change
    • Physical appearance changes, but composition remains the same (e.g., freezing, melting, evaporation).
  • Chemical change
    • Substances undergo chemical change to form new substances (e.g., iron rusting, copper oxidizing).

Compounds, Ions, and Elements

  • Compound
    • Distinct substance, chemically combined in definite proportion by mass (e.g., \text{H}2\text{O},\ H2\text{O}_2).
    • Can be decomposed into simpler pure substances by chemical means (e.g., \text{FeS} \rightarrow \text{Fe} + \text{S}).
  • Types of compounds
    • Molecules or Covalent compounds (e.g., \mathrm{H2O},\ \mathrm{H2O_2}).
    • Ionic compounds (e.g., \mathrm{NaCl},\ \mathrm{MgCl_2}).
  • Molecule (Covalent compound)
    • A group of two or more atoms that function as a unit because of tight bonding.
    • Homoatomic molecules: all atoms in the molecule are the same (e.g., \mathrm{O_2}).
    • Heteroatomic molecules: two or more kinds of atoms present (e.g., water: \mathrm{H_2O}).
    • Diatomic molecules: two atoms of the same kind (e.g., \mathrm{H2},\ \mathrm{O2},\ \mathrm{N_2}).
  • Ions
    • Atom or group of atoms that is electrically charged due to loss or gain of electrons.
    • Cations: atoms that have lost electrons; positively charged (e.g., \mathrm{Li^+},\ \mathrm{Ca^{2+}}).
    • Anions: atoms that have gained electrons; negatively charged (e.g., \mathrm{Cl^-},\ \mathrm{O^{2-}}).
    • A neutral atom has equal numbers of protons and electrons.
  • Element
    • Fundamental substance that cannot be broken down into simpler substances by chemical or physical means.
    • Pure substance with fixed composition by mass (e.g., metals: \text{Cu},\ \text{Ag},\ \text{Au},\ \text{Fe}).
    • Periodic Table: Elements are written with uppercase letters and, for many, a lowercase letter following (e.g., \mathrm{Na},\ \mathrm{Ca},\ \mathrm{Fe}).
    • Some elements are written with a single uppercase letter only (e.g., \mathrm{H},\ \mathrm{O},\ \mathrm{N}).

Periodic Table of Elements

  • Classification of elements
    • Representative elements: Groups IA, IIA, IIIA–VIIIA (main-group elements).
    • Noble gases: Group VIIIA (noble gases).
    • Transition elements: Groups IIIB–VIIIB, IB, IIB (transition metals).
    • Inner transition elements: Lanthanides and Actinides (the f-block).
  • Metals vs Nonmetals vs Metalloids
    • Metals: generally solid at room temperature (except mercury), high luster, good conductors of heat and electricity, malleable, ductile, typically high melting points.
    • Nonmetals: non-lustrous, poor conductors, brittle, nonmalleable, typically lower melting points.
    • Metalloids: exhibit properties intermediate between metals and nonmetals.
  • Element naming conventions
    • Elements are denoted by chemical symbols (1- or 2-letter codes, first letter capitalized, second letter lower-case if present).
    • Examples: \mathrm{H} (hydrogen), \mathrm{He} (helium), \mathrm{Na} (sodium), \mathrm{Ca} (calcium), \mathrm{Fe} (iron).
  • Periodic table layout (conceptual)
    • Groups (columns) share chemical properties.
    • Periods (rows) indicate energy levels or shell filling tendencies.
    • Location helps predict properties like reactivity and conductivity.
  • Real-world relevance and connections
    • Knowledge of states of matter informs everyday phenomena (melting/freezing, boiling/condensation).
    • Understanding substances vs mixtures is essential for chemistry lab safety and material preparation.
    • Ionic vs covalent bonding underpins properties of salts, acids, bases, and polymers.

Summary of Key Formulas and Notation

  • Atomic and molecular formulas
    • Water: \mathrm{H_2O}
    • Hydrogen peroxide: \mathrm{H2O2}
    • Sodium chloride: \mathrm{NaCl}
    • Oxygen gas: \mathrm{O_2}
    • Diatomic elements: \mathrm{H2},\mathrm{O2},\mathrm{N2},\mathrm{Cl2},\mathrm{Br2},\mathrm{I2},\mathrm{F_2}
  • Ion charges
    • Cations: \mathrm{Li^+},\ \mathrm{Ca^{2+}}
    • Anions: \mathrm{Cl^-},\ \mathrm{O^{2-}}
  • Temperature references
    • Sun surface temperature: 6\times 10^3\,^{\circ}\mathrm{C}
  • Size reference
    • Atomic size estimate: 4\times 10^{-9}\ \text{inches}

Notes on structure and terminology

  • Pure substances have fixed composition and single phase; mixtures have variable composition and may have multiple phases.
  • Physical properties are observed without changing composition; chemical properties describe potential chemical changes.
  • Physical changes are generally reversible; chemical changes yield new substances (often not easily reversible).
  • The diatomic mnemonic HONClBrIF helps recall diatomic elements: Hydrogen, Oxygen, Nitrogen, Chlorine, Bromine, Iodine, Fluorine.
  • The periodic table organizes elements by properties and electron structure, with metals, nonmetals, metalloids, and noble gases forming distinct families.