Overview
This lecture explains how to separate mixtures using filtration, evaporation, and crystallization, focusing on the key differences between insoluble and soluble solids in mixtures.
Types of Mixtures
- A mixture contains two or more substances together in the same place without chemical joining.
- Mixing an insoluble solid (one that cannot dissolve) with a liquid creates a suspension, like sand and water.
- Solutions are formed when a soluble solid (solute) dissolves in a liquid (solvent), such as salt in water.
Filtration: Separating Insoluble Solids from Liquids
- Filtration is used to separate insoluble solids from liquids.
- Filter paper allows only liquid to pass through, trapping the solid on the paper.
- The mixture is poured through a filter funnel lined with filter paper.
Evaporation and Crystallization: Separating Soluble Solids from Liquids
- Filtration does not work with solutions as the solid is dissolved.
- Evaporation involves heating the solution until the solvent evaporates, leaving dry crystals of the solute.
- Evaporation is quick but not suitable for solids that decompose when heated (thermal decomposition).
- Crystallization is used for heat-sensitive solids: heat the solution gently, stop heating when crystals form, cool to form more crystals, then filter and dry the crystals.
Key Terms & Definitions
- Mixture — two or more substances physically combined but not chemically bonded.
- Insoluble solid — a substance that cannot dissolve in a liquid.
- Solute — the substance that dissolves in a solvent to form a solution.
- Solvent — the liquid that dissolves a solute to form a solution.
- Solution — a mixture where the solute is fully dissolved in the solvent.
- Filtration — a method to separate insoluble solids from liquids using filter paper.
- Evaporation — separating a soluble solid from a solution by heating to remove the solvent.
- Crystallization — gently heating a solution to form and collect pure crystals of the solute.
- Thermal decomposition — breaking down of a substance by heat.
Action Items / Next Steps
- Review filtration, evaporation, and crystallization techniques.
- Practice identifying suitable separation methods for given mixtures.
- Study definitions of key terms.