chemistry

• Sedimentation is where heavier particles settle at the bottom of the liquid because of gravity, leaving the lighter particles or liquid on top. This is often used to clean dirty water. Here you make use of the difference in density of the substance in the mixture.
• Filtration, the process in which solid particles in a liquid or gaseous fluid are removed by the use of a filter medium that permits the fluid to pass through but retains the solid particles. Here you make use of the difference in particle size of a substance from a mixture.
• Extraction: this is where a substance is moved from one liquid to another because it dissolves better in the second liquid. This is used a lot in labs and factories to get specific parts out of a mixture. When extracting, add a solvent to a mixture of substance, which is known as the extraction agent that extracts one substance from the other one. In the case of sand and salt, you use water as the extraction agent.
• Evaporation is a method where a liquid is heated until it turns into vapour. This seperates the liquid from any solid stuff that was dissolved in it. It's used to get salt from seawater and to clean liquids. Here you can make use of the difference in solubility.
• Distillation is a technique where a liquid mixture is heated until it boils and turns into vapour. The vapour is then cooled to become liquid again in a different container. This seperates the parts of the mixture that boil at different temperatures. It's used to make distilled drinks and clean chemicals. Here you make use of the difference in boiling point.
• Adsorption is when a substance sticks to the outside of something else. You can remove one or more substances from a mixture of solutions or gases and for this seperation method, you need an adsorption agent. The mixture you want to seperate is passed along the adsorption agent. The mixture you want to get rid of is bound (attached) to the surface of the adsorption agent. A widely used adsorption agent is activated charcoal (Norit). Here you make use of the difference in adhesion (how well something can sticks to a surface).
• Rf-value= distance travelled by substance/ distance travelled by solvent
• chromatography = a seperation method that uses the difference in adhesion and solubility.
• In paper chromatography, the mobile phase is the solvent that moves through the paper because it moves and the stationary phase is the paper because it remains in its place.
• Gas chromatography

  • takes place in a long tube called a column, through which a gas flows at a constant speed.
  • Gas is the mobile phase and on the inside of the column is the stationary phase.
  • the time a substance spends in a column is called the retention time.
• The solubility of a substance is the maximum number of grams that can dissolve in one litre of solvent at a certain temperature.

  A saturated solution is a solution in which the maximun amount of a substance is dissolved.

  A unsaturated solution is a solution in which less than the maximum is dissolved.

  In liquids and solids, the solubility increases as the temperature of hte solution increases. However, the solubility of gases decreases as the temperature of the solution increases.
• Covalence is the number of bonds with other atoms in a molecule
• isomers = same molcular formula but different structural formula