States of Matter and Mixtures: Filtration and Crystallisation

Filtration: This is a method used to separate mixtures composed of a solid and a liquid. A philtre paper or other porous material is used to allow the liquid to pass through, leaving behind the solid.
Filtration is often used when the solid component of a mixture is unwanted or when the liquid component is needed.
Crystallization: This process is used to separate a solute from a solution. It’s commonly used when the solute is desirable, and the solvent isn’t, or when a purer solute is needed.
To perform a crystallisation, a solution is heated to evaporate some of the solvent and increase the concentration of the solute. If the heating is then stopped, the hot solution will begin to cool.
As cooling occurs, the solute will no longer dissolve in the solvent and will begin to form crystals. These crystals can then be separated from the liquid through filtration.
Rapid crystallisation can be induced by scratching the inside of the container containing the solution, or introducing a small ‘seed’ crystal.
Crystallisation can also be used to purify substances, as impurities are generally not included in the crystal structure and remain dissolved in the solution.
Crystallisation is an example of a physical change; the original properties of the substance are retained after the process.
Both filtration and crystallisation are important in chemical labs for purifying and isolating various compounds.
Evaporating the solvent too quickly can lead to the formation of small crystals, while slow evaporation can produce larger and purer crystals.
The remaining liquid after crystallisation, known as the ‘mother liquor’, often contains impurities or additional solute.
There are many real-world applications of these techniques, for example, in the purification of water, the formation of salt crystals, and the manufacture of various chemical products.