Overview
This lecture introduces the fundamental concepts of chemistry, focusing on matter, its classification, and the distinction between elements, compounds, and mixtures.
Introduction to Chemistry and Matter
- Chemistry studies the interactions of matter (made of atoms) and energy.
- Matter is classified as mixtures or pure substances.
Classification of Matter
- Pure substances are further divided into elements and compounds.
- Mixtures are classified into heterogeneous and homogeneous mixtures.
- Pure substances also exist in different phases: solid, liquid, and gas.
Pure Substances: Elements and Compounds
- An element is a pure substance made of one type of atom, found on the periodic table.
- Compounds are pure substances made from atoms of different elements bonded in fixed proportions.
- Examples of elements: Gold (Au), Oxygen gas (O₂), Liquid nitrogen (N₂), Helium (He).
- Examples of compounds: Water (H₂O), Sucrose (C₁₂H₂₂O₁₁), Table salt (NaCl).
- Compounds have properties distinct from their constituent elements.
Mixtures: Types and Characteristics
- Mixtures consist of two or more pure substances that retain their individual properties.
- Components of mixtures can be separated by physical methods.
- Examples of mixtures: Syrup, air, milk, salads.
Homogeneous vs. Heterogeneous Mixtures
- Homogeneous mixtures have uniform composition throughout (e.g., homogenized milk, orange juice without pulp, brewed coffee).
- Heterogeneous mixtures have visibly different components (e.g., fresh milk, chicken noodle soup, nut mixtures, orange juice with pulp).
Phases of Matter
- Gases: No definite shape or volume; fill container (e.g., steam, oxygen gas).
- Liquids: Definite volume, shape of container (e.g., water, gasoline, olive oil).
- Solids: Definite shape and volume (e.g., ice, salt, wood, granite).
Practice Questions Review
- Sodium chloride: compound (pure substance).
- Neon gas: element (pure substance).
- Liquid mercury: element (pure substance).
- Alumina: compound (pure substance).
- Iodine crystals: element (pure substance).
- Diamond: element (pure substance).
- Cottage cheese: mixture.
- Iron metal: element (pure substance).
- Soil: mixture.
- Casserole: mixture.
- Sodium chloride in water: homogeneous mixture.
- Veins of gold in rock: heterogeneous mixture.
- Casserole: heterogeneous mixture.
- Soapy water: homogeneous mixture.
- Water with ice cubes: heterogeneous mixture (different phases).
Key Terms & Definitions
- Element — Pure substance of one type of atom, listed on the periodic table.
- Compound — Pure substance of two or more atoms bonded in fixed proportions.
- Mixture — Two or more pure substances mixed, each retaining its identity.
- Homogeneous mixture — Mixture uniform throughout, also called a solution.
- Heterogeneous mixture — Mixture with visibly different components.
- Phase of matter — Physical state: solid, liquid, or gas.
Action Items / Next Steps
- Practice identifying substances as elements, compounds, or mixtures.
- Review the definitions and examples of homogeneous and heterogeneous mixtures.
- Be prepared to classify matter in homework or quizzes.