Overview
This lecture covers the two main types of mixtures, five separation techniques used in chemistry, and sets the stage for discussing laws of mass and atomic theory in future sessions.
Types of Mixtures
- Chemists commonly encounter two types of mixtures: heterogeneous and homogeneous mixtures.
- Heterogeneous mixtures have visible boundaries between components (e.g., oil and water, mixed candy).
- Heterogeneous mixtures can be separated by physical means such as filtration or picking apart by hand.
- Homogeneous mixtures appear uniform throughout with no visible boundaries (e.g., dissolved sugar in Kool-Aid).
- When homogeneous mixtures are liquids, they are called solutions, specifically aqueous solutions if water is the solvent.
Separation Techniques
- Filtration separates mixtures based on particle size; only smaller particles pass through the filter.
- Crystallization purifies substances based on differences in solubility by forming crystals from a solution.
- Distillation separates components based on differences in volatility (boiling points); the more volatile component boils off first.
- Extraction separates substances based on solubility in different solvents; one component dissolves while another remains solid.
- Chromatography separates components by differences in solubility using a solvent to carry different substances at different rates.
Key Terms & Definitions
- Heterogeneous Mixture — a mixture with visibly different parts or phases.
- Homogeneous Mixture — a mixture with a uniform appearance and properties throughout.
- Solution — a homogeneous mixture, often a liquid, where one substance is dissolved in another.
- Filtration — separation technique using a barrier to separate particles by size.
- Crystallization — purifying a substance by forming solid crystals from a solution.
- Distillation — separating mixtures by boiling and condensing components with different volatilities.
- Extraction — separating components based on solubility in a particular solvent.
- Chromatography — separation based on differential solubility and movement through a medium.
Action Items / Next Steps
- Prepare for problem-solving exercises on mixtures and separation techniques in the next class.
- Review definitions and examples of heterogeneous and homogeneous mixtures.
- Be ready to apply separation techniques to laboratory scenarios.