Junior Cert Science - Mixtures
- A mixture consists of two or more elements which are mixed together but are not chemically combined.
- Examples of mixtures are air (a mixture of gases) and seawater (a mixture of water & salt).
- Crystillisation is when crystals are formed from a solution which is evaporated.
- Filtration is used to separate insoluble solids from liquids. The mixture is passed through filter paper, which traps the solids and allows the liquid to pass through.
- Evaporation is used to separate soluble solids from liquids. The liquid is evaporated, leaving the solid behind.
- Distillation is used to separate two liquids with different boiling points, e.g. water and alcohol. It can also be used to separate soluble solids from liquids.
- Chromotography is used to separate a mixture of dissolved substances in a solution.
- A solution is a mixture of a solute (substance which is dissolved) and a solvent (liquid in which the solute is dissolved), e.g. copper sulfate dissolved in water.
- The hotter the solvent, the more solute will dissolve in it.
- A concentrated solution has a large amount of solute dissolved in a small amount of solvent. A dilute solution has a small amount of solute dissolved in a large amount of solute.
- A saturated solution is one which has the maximum possible amount of dissolved solute at that temperature.
- A dilute solution can be made concentrated by adding more solute or evaporating off some of the solvent. A concentrated solution can be made more dilute by adding more solvent.
- When a saturated solution is cooled to a lower temperature, crystals of the solute form. This is known as crystallisation. For example, when a concentrated solution of copper sulfate in water is cooled, copper sulfate crystals form.