Chemical Elements, Compounds & Mixtures

Elements and Compounds

• Elements: Substances made of one kind of atom and cannot be chemically broken down.
• In reactions, elements combine in fixed ratios to form compounds.
• Compounds: Made from two or more elements chemically bonded; properties differ from constituent elements.

Example

• Sodium chloride (NaCl) has different properties from sodium (Na) and chlorine (Cl).

Mixtures

• Mixtures: Contain multiple elements/compounds not chemically combined.
• Components retain properties of their pure form.

Types of Mixtures

• Homogeneous Mixture:
  • Uniform composition and properties (e.g., air, bronze).
• Heterogeneous Mixture:
  • Non-uniform composition, different properties throughout (e.g., concrete, orange juice with pulp).
  • Components can often be visibly identified.

Separating Mixtures

• Components retain individual properties, allowing separation based on physical properties such as:
  • Boiling point
  • Solubility
  • Magnestism
  • Density

Example: Salt and Sand

• Add water: salt dissolves, sand does not.
• Filtration: Salt solution passes through as filtrate, sand is residue.
• Evaporation: Remove water to recover salt.

Terms

• Element: Basic substance that cannot be broken down.
• Compound: Made of two or more elements in a fixed ratio.
• Mixture: Combination of substances that retain their properties.
• Homogeneous: Uniform composition.
• Heterogeneous: Non-uniform composition.