What Are The Types Of Pure Substances?

Key Notes:

Definition of Pure Substances:

• Pure substances consist of only one type of particle (atoms or molecules).
• They have a uniform and definite composition throughout.

Types of Pure Substances:

• Elements:
  • Made up of only one type of atom.
  • Cannot be broken down into simpler substances by chemical means.
  • Examples: Oxygen (O₂), Gold (Au), Hydrogen (H₂).
• Compounds:
  • Formed by the chemical combination of two or more elements in a fixed ratio.
  • Can be broken down into simpler substances by chemical means.
  • Examples: Water (H₂O), Sodium Chloride (NaCl), Carbon Dioxide (CO₂).

Characteristics of Elements:

• Exist as metals, non-metals, and metalloids.
• Examples:
  • Metals: Iron (Fe), Aluminum (Al).
  • Non-Metals: Carbon (C), Sulfur (S).
  • Metalloids: Boron (B), Silicon (Si).

Characteristics of Compounds:

• Have properties different from their constituent elements.
• Always combine in a fixed ratio by mass (Law of Definite Proportions).
• Examples:
  • Water (H₂O): Made of hydrogen and oxygen, but different properties from both.
  • Carbon Dioxide (CO₂): Combines carbon and oxygen in a 1:2 ratio.

Differences Between Elements and Compounds:

Property	Elements	Compounds
Composition	One type of atom	Two or more types of atoms
Separation Methods	Cannot be broken down	Can be broken into elements
Examples	Oxygen (O₂), Copper (Cu)	Water (H₂O), Sodium Chloride (NaCl)

Importance of Pure Substances:

• Used in scientific research for consistency.
• Essential in manufacturing, like making medicines and alloys.

Testing Purity:

• Pure substances have specific melting and boiling points.
• Impurities alter these properties.

Everyday Examples:

• Elements: Aluminum foil, oxygen gas.
• Compounds: Salt in food, sugar in drinks.