Overview
This lecture explains methods for separating mixtures, focusing on filtration for insoluble solids and evaporation or crystallization for soluble solids in solutions.
Key Terminology for Mixtures
- A mixture consists of two or more substances not chemically joined.
- An insoluble solid does not dissolve in a liquid (e.g., sand in water).
- A solution is made when a solute (dissolved substance, like salt) mixes with a solvent (liquid, like water).
Filtration: Separating Insoluble Solids from Liquids
- Filtration separates insoluble solids from liquids using filter paper and a funnel.
- Filter paper allows the liquid to pass through but traps solid particles.
- This is used when solids can't dissolve in liquids.
Evaporation: Separating Soluble Solids from Solutions
- Evaporation removes the solvent by heating the solution until only the solid remains.
- An evaporating dish or crucible is used for heating, often with a Bunsen burner.
- This technique works quickly but may break down some solids if they decompose with heat (thermal decomposition).
Crystallization: Separating Soluble Solids Without Decomposition
- Crystallization gently heats the solution, often with a water bath, to avoid decomposing the solid.
- Once some solvent evaporates and crystals start to form, heating stops and the solution is left to cool.
- More crystals form as the solution cools due to decreased solubility.
- Crystals are then filtered out and dried, either in a warm place or a drying oven.
Key Terms & Definitions
- Mixture — combination of substances not chemically joined.
- Insoluble solid — a solid that cannot dissolve in a liquid.
- Solution — a homogeneous mixture of a solute dissolved in a solvent.
- Filtration — method to separate insoluble solids from liquids.
- Evaporation — removal of solvent by heating to leave behind a solid.
- Crystallization — slow formation of solid crystals as a solution cools.
- Thermal decomposition — breakdown of a substance when heated.
Action Items / Next Steps
- Review the definitions and examples of mixtures, solutions, and separation techniques.
- Practice explaining when to use filtration, evaporation, or crystallization.
- Complete any related exam-style questions or flashcards on the website.