Classifying Matter: Elements, Compounds, and Mixtures

Classifying Matter - Elements, Compounds, and Mixtures

Pure Substances

• A pure substance is a sample of matter with definite chemical and physical properties.
• Pure substances can be elements or compounds.
  • Elements consist of atoms.
  • Compounds consist of molecules.

Elements

• An element is a pure substance that cannot be separated into simpler substances by physical or chemical means.
• Elements are organized in the Periodic Table of the Elements.

Compounds

• A compound is a pure substance composed of two or more different elements joined by chemical bonds.
• The elements in a compound are in a specific ratio that is always the same.
• Compounds have a chemical formula.
• Compounds can only be separated by chemical means, not physically.
• Examples:
  • Water: H_2O
  • Carbon dioxide: CO_2
  • Sodium chloride: NaCl

Composition of Compounds

• A compound is made from more than one element.
• Examples:
  • A compound made up of 2 different elements.
  • A compound made up of 7 different elements.

Breaking Down Compounds

• A compound can be broken down into elements.
• Examples:
  • A compound made up of 3 different elements.
  • An element.
  • An element.
  • An element.

Arrangement of Particles

• Molecules: Small groups of atoms bonded together (e.g., H2, CO2).
• Lattices: Repeating structures with many atoms bonded in a regular pattern (e.g., NaCl – table salt).
• Compounds can exist as molecules or lattices, depending on the elements involved.

Molecules

• Molecules consist of two or more atoms held together by chemical bonds.
  • Elemental molecules: Contain only one type of element (e.g., Oxygen O2, Helium He, Chlorine Cl2, Nitrogen N_2).
  • Compounds: Contain different elements (e.g., Carbon Dioxide CO2, Water H2O).

Examples of Lattice Structures

• Metallic Lattices (e.g., Cu Lattice)
• Ionic Lattices
• Covalent Lattices

Mixtures

• A mixture is a combination of two or more pure substances that are not chemically combined.
• Substances in a mixture are held together by physical forces, not chemical bonds.
• No chemical change takes place in a mixture.
• Each substance in the mixture retains its properties.
• Mixtures can be separated physically.

Mixtures vs. Compounds

Identifying Materials

• Water: Compound (Hydrogen and Oxygen)
• Coal: Mixture (Carbon, hydrogen, sulfur, volatile impurities & moisture)
• Carbon dioxide: Compound (Carbon and Oxygen)
• Oxygen: Element (Oxygen)
• Chalk: Compound (Calcium carbonate - Calcium, Carbon & Oxygen)
• Wax: Compound (Carbon & Hydrogen)
• Table salt: Compound (Sodium & Chlorine)
• Caffeine: Compound (Carbon, Hydrogen, Nitrogen & Oxygen)

Element, Compound, or Mixture?

• Rocks: Mixture
• Copper (Cu): Element
• Jelly Beans: Mixture
• Table Sugar (C{12}H{22}O_{11}): Compound
• Diamond (C): Element
• Tea: Mixture
• Salt (NaCl): Compound
• Neon Gas (Ne): Element
• Salad: Mixture
• Pure Water (H_2O): Compound
• Aluminum (Al): Element
• Lemonade: Mixture
• Silver (Ag): Element
• Sand: Mixture

Flow Chart Summary

• Matter can be classified as either a pure substance or a mixture.
• Pure substances can be further classified as elements or compounds.
• Mixtures can be classified as homogeneous or heterogeneous.
• Examples:
  • Element: He (Helium)
  • Compound: Pure water
  • Homogeneous Mixture: Tea with sugar
  • Heterogeneous Mixture: Wet sand