Overview
This lecture covers physical separation techniques in chemistry, specifically filtration and crystallization, and explains when and how to use each method to separate mixtures.
Physical Separation Techniques
- Physical separation techniques are used to separate mixtures, not compounds.
- Chemical methods such as reduction or electrolysis are needed to separate elements in compounds.
Filtration
- Filtration separates an insoluble solid from a liquid.
- An insoluble solid does not dissolve in a liquid.
- Example: Silver chloride (solid) does not dissolve in water (liquid).
- A filter funnel and filter paper are used for filtration.
- The liquid that passes through the filter paper is called the filtrate.
- The solid gets trapped in the filter paper.
Crystallization
- Crystallization separates a soluble solid from a liquid.
- A soluble solid can dissolve in a liquid to form a solution.
- Example: Sodium chloride (salt) dissolves in water to form an aqueous solution.
- Leaving the solution for several days allows the water to evaporate, leaving solid crystals behind.
- The process can be sped up by gently heating, but some chemicals may decompose if heated.
Key Terms & Definitions
- Mixture — combination of substances that are not chemically bonded.
- Insoluble — a substance that does not dissolve in a liquid.
- Soluble — a substance that dissolves in a liquid.
- Filtration — process of separating an insoluble solid from a liquid using filter paper.
- Filtrate — the liquid that passes through the filter paper during filtration.
- Crystallization — process of obtaining solid crystals from a solution by evaporating the liquid.
- Aqueous (aq) — describes a substance dissolved in water.
- State symbols — notations (s, l, g, aq) indicating the physical state of a chemical.
Action Items / Next Steps
- Practice questions on filtration and crystallization.
- Review solubility tables if needed for exams.