 A solution is a mixture of two or more substances in the same phase. This is formed when a solute dissolves in a solvent. A solution can also be formed when two or more miscible liquids are mixed together. When ethanol and water are mixed together, a solution is formed. Now how would we separate these solutions? To separate dissolved salt from water, we would simply evaporate as much water as possible, leaving behind white salt crystals. The separation technique is known as evaporation. To separate ethanol from water, we must take into account the fact that these substances have very different boiling points. Water boils at 100 degrees Celsius, whereas ethanol boils at 78 degrees Celsius. This mixture can be separated by simple distillation. The lower boiling point component, in our case, ethanol, will evaporate first. The ethanol vapor condenses as it passes through the condenser, and the distilled ethanol can then be collected in the receiving flask. The above mixtures are homogenous mixtures. This means that the components of the mixture are in the same phase, or the composition of the mixture is uniform throughout. Now we will look at separating heterogeneous mixtures, where the components in the mixture are not in the same phase, or the composition of the mixture is uneven. If we have a mixture of sulfur and iron filings, we can easily separate this mixture with a magnet. The magnet will remove all of the iron filings, leaving behind the yellow sulfur powder. We know that salt is completely soluble in water, but sand is not. How would you separate a mixture of salt and sand easily, keeping in mind the solubility of salt and water? Pause, think, and continue when you have an answer. The salt and sand mixture can be added to water. Salt will dissolve, but sand cannot. The resulting heterogeneous mixture can be filtered through a funnel lined with filter paper, and washed with water to remove as much salt as possible. The substance that remains on the filter paper is known as the residue, and the substance collected in the flask is called the filtrate. For our case, sand is the residue, and the salt water is the filtrate. The salt can be obtained using evaporation, and the sand left to dry. The same method is used to separate a suspension, which is a mixture of an insoluble solid in a liquid, such as, for example, small bits of chalk in water. To emissable liquids, such as oil and water, can be separated using a separatory funnel. This is an apparatus with a stopcock at the bottom. Releasing the stopcock allows the contents to flow out, and closing it stops the flow. To summarize, there are many different techniques to separate mixtures, all depending on whether the mixture is homogenous or heterogeneous.