Crystallization
Key Notes :
What is Crystallization?
- Crystallization is the process by which a solid forms, where the atoms or molecules are arranged in a highly ordered structure known as a crystal.
- It is often used to separate a pure substance from a solution.
How Crystallization Works
- Dissolution: A solid (solute) is dissolved in a solvent (like water) to form a solution.
- Cooling or Evaporation: The solvent is slowly evaporated or the temperature is lowered, causing the solute to come out of the solution and form crystals.
- Formation of Crystals: The solute molecules or ions arrange themselves in a repeating pattern to form a crystal lattice.
Types of Crystallization
- Evaporative Crystallization:
- Involves evaporating the solvent to allow crystals to form.
- Common in nature, like in the formation of salt crystals from seawater.
- Coolant Crystallization:
- Involves cooling the solution, which causes the solute to form crystals.
- Often used in the laboratory.
Examples of Crystallization
- Salt Crystals: When seawater evaporates, salt crystals form.
- Sugar Crystals: Crystallization of sugar is seen in candy making or when making rock candy.
Importance of Crystallization
- Purification: Crystallization is used in laboratories and industries to purify substances.
- Extraction: It is a useful method for extracting pure substances from mixtures.
- Industrial Applications: Used in the production of substances like sugar, salt, and other minerals.
Factors Affecting Crystallization
- Concentration: The more concentrated the solution, the more solute will crystallize.
- Temperature: Lower temperatures often result in crystallization.
- Rate of Cooling: Slow cooling allows larger crystals to form, while rapid cooling results in smaller crystals.
Key Points to Remember
- Crystallization helps in obtaining pure substances from mixtures.
- It occurs when the solvent is removed or the solution is cooled.
- The resulting crystals are usually very pure, as impurities are left behind in the solution.
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