Filtration filtration can be used to separate insoluble solids from liquids
Filter funnel and filter paper are used
- Liquid that passes through filter paper → filtrate
- Solid that remains on the filter paper - residue
Evaporation to Dryness Substances with lower boiling points will turn into gas first, leaving other substances behind. Difference in boiling point can be used to separate the dissolved solute from the solvent. To collect the dissolved solid(solute) from a solution, we simply heat the solution in an evaporating dish until all the liquid(solvent) evaporates, and we are left with the solid.
- Evaporation to dryness can be used to separate a dissolved solid from its solvent by heating the mixture until all the solvent has evaporated.
Solute must have a high melting point → does not decompose easily when heated strongly.
Crystallization If solute decomposes or breaks down into simpler substances when heated, a gentler method called crystallization is used instead.
- crystallization can be used to obtain pure solid from its saturated solution
- a saturated solution is one in which no more solute can be dissolved
- Gently heat the copper(II)sulfate solution in an evaporating dish to evaporate most of the liquid, until the solution is saturated. Stop heating the solution before all the solvent has evaporated.
- Cool the solution gradually until the solid copper(II)sulfate crystals appear within the solution.
- Carefully pour the mixture (solution with the crystals) through a funnel lined with filter paper to collect the solid crystals. If more crystals are required, filtrate is re concentrated and recrystallized (repeat steps 1-3)
- copper(II)sulfate crystals are washed with some cold distilled water to remove impurities. They can be dried between a few sheets of filter paper.** For most substances, solubility increases with temperature, so cooling a saturated solution will result in crystallization.
How to tell if the solution is saturated?
⇒ insert a clean glass rod and remove it.
On its tip → a small amount of solution will be on the rod.
If small crystals form on the rod as the solution cools, the solution is said to be saturated/has reached its saturation point.
Simple Distillation Relies on the solid and liquid components in a mixture having different boiling points.
- Simple distillation is used to separate a pure solvent(liquid) from a solution *Unlike evaporation - liquid that is vaporized is collected by condensation so both solute and solvent can be obtained.
- Salt water is heated. Boiling chips are added for smooth boiling. At 100 degree Celsius, water boils(and vaporizes). Vapor rises and enters the condenser through the exit sidearm of the distillation flask.
- Water vapor cools in the condenser(condenser cools water vapor) and condenses back to liquid water. Pure water is collected in a conical flask as the distillate.
- As more water vaporizes, salt solution becomes more concentrated. Eventually, a solid residue of salt remains in the distillation flask. (solute and other impurities are left behind in the distilling flask)
- Thermometer with its mercury bulb placed next to the mouth of the condenser that is connected to the distilling flask, reads the boiling point of the distillate.
Miscible liquids are those which form a uniform (homogeneous) solution when mixed together
- heterogeneous mixture contains immiscible liquids
- When a heterogeneous mixture of two or more immiscible liquids are left undisturbed, they can separate into layers known as phases. The least dense liquid makes up the top phase. Densest liquid will be at the bottom.