Chemistry: Matter and Its Properties

What is Chemistry?

  • Chemistry is the study of
    • Composition of matter
    • Structure and properties of matter
    • Processes that occur and energy changes in matter

Definition of Key Terms

  • Chemical: Any substance with a definite composition
    • Examples:
    • Sucrose (C₁₂H₂₂O₁₁)
    • Water (H₂O)
    • Carbon Dioxide (CO₂)

Understanding Matter

  • Matter: Anything that has mass and occupies space
  • Volume: The amount of space an object occupies
  • Mass: A measure of the amount of matter

Basic Building Blocks of Matter

  • Atom: The smallest unit of an element that maintains the chemical properties of that element.
  • Element: A pure substance made of only one type of atom.
  • Compound: A pure substance composed of two or more different elements that are chemically combined.

Properties of Matter

Physical Properties
  • Observed or measured without changing the substance's identity
    • Examples: melting point, boiling point, density, color, mass
Intensive Properties
  • Do not depend on the amount of matter present
    • Examples: melting point, boiling point, density, ability to conduct electricity
Extensive Properties
  • Depend on the amount of matter present
    • Examples: volume, mass, energy content
Chemical Properties
  • Describe the substance’s ability to undergo changes
    • Example: Reaction with acid or air

Changes in Matter

Physical Changes
  • Changes that do not involve a change in the identity of the substance
    • Examples: grinding, cutting, melting, boiling
  • Change of state: A physical change of a substance from one state to another (solid, liquid, gas)
Chemical Changes
  • Occur when one or more substances transform into new substances with different properties
    • Examples: burning, tarnishing, digesting
  • Reactants: Substances that undergo a chemical change
  • Products: Substances formed by the chemical change
    • Example: Carbon + Oxygen yields Carbon Dioxide
      C + O2 ightarrow CO2

Evidence of a Chemical Change

  • Change in color, formation of gas, precipitate formation, temperature change, or occurrence of light

Particle Model of Matter

  • Different states of matter: solid, liquid, gas, plasma
    • In solids, particles are closely packed in fixed positions
    • In liquids, particles are close but can move freely
    • In gases, particles are far apart and move freely
    • In plasma, ions and electrons move independently

Introduction to the Periodic Table

  • Groups (Families): Vertical columns in the periodic table, elements share similar properties.
  • Periods: Horizontal rows in the periodic table, show increasing atomic number.

Characteristics of Elements

Metals
  • Properties: mostly solid at room temperature, malleable, ductile, good conductors of electricity and heat
    • Examples of metals: Gold (Au), Copper (Cu), Aluminum (Al)
Nonmetals
  • Properties: many are gases or brittle solids, poor conductors of heat and electricity
    • Examples of nonmetals: Carbon (C), Sulfur (S), Phosphorus (P), Iodine (I)
Metalloids
  • Elements that have both metallic and non-metallic properties
    • Properties: All are solids at room temperature, semiconductors of electricity
Noble Gases
  • Elements in Group 18 of the periodic table, generally unreactive, gases at room temperature.