Mixtures, Solutions, Suspensions and Colloids free essay sample

Some colloids are translucent which causes particles to be scattered throughout the colloid, whilst other colloids may be opaque or have a slight color. PROPERTIES (Particle Visibility, Particle Distribution, Filterability, Particle Size, Nature, Appearance) SOLUTION Not visible to the Naked Eye Even throughout/Completely dissolved Not be easily separated Technically small Homogeneous Transparent SUSPENSION Easily seen with the Naked Eye Equally dispersed/ Not dissolved at all Easily separated Large Heterogeneous Opaque COLLOID Hard spotting with The Naked Eye Undissolved particles /Partially dissolved Not easily separated Intermediate Heterogeneous Translucent TABLE SHOWING PROPERTIES OF DIFFERENT TYPES OF MIXTURES METHODS OF SEPARATION There are several methods of separation. These methods vary based on whether the components are solid, liquid or gas. The most common known methods are as follows: 1. Distillation 2. Separating funnel 3. Filtration 4. Solvent extraction 5. Paper chromatography 6. Recrystalization 7. Evaporation 8. Sublimation DISTILLATION This is defined as the process of boiling a liquid and condensing and collecting the vapor. The liquid is collected in a distillate. It is used to purify liquids and to separate liquid mixtures. There are two main forms of distillation which are simple distillation and fractional distillation. SIMPLE DISTILLATION This is used to obtain a pure solvent from a solution; for example, pure water from sea water. The impure liquid is heated until evaporation which will produce a pure vapor. This vapor is condensed by cooling and the pure liquid is obtained. FRACTIONAL DISTILLATION This is used with liquids of similar boiling points. Effective separation can be achieved by using a fractionating column attached to the distillation vessel and filled with glass beads. Vapor from the liquid rises up the column until it condenses and runs back into the vessel. The rising vapor in the column flows over the descending liquid. The vapor in the column has more volatile components towards the top and the less volatile components at the bottom. Various fractions of the mixture can be drawn of the mixture can be drawn off at points on the column. SEPARATING FUNNEL One can use a separating funnel to separate a pair of immiscible liquids. This is due to the distinct layers between the two liquids, in which the more dense liquid will be at the bottom, while the less dense liquid will be at the top. FILTRATION This is defined as a method of separating suspended solids from liquids, which in this case means both liquids and gases. The solid may be an impurity to be removed from a liquid product, or the desired product, so the liquid can be discarded. The separation of water from soil can be an example where this type of separation can be used. A filter paper is used in the process of separation. When pressure is applied to the mixture, the solvent is pushed through a semi-permeable membrane which is the filter paper. The solute is then trapped in the filter paper whilst the solvent passes through, thus separating the former mixture. SOLVENT EXTRACTION This is defined as the process of separating one constituent from a mixture by dissolving it in a solvent in which it is soluble but in which the other constituents of the mixture are not. The process is usually carried out in the liquid phases, in which case it is also known as liquid-liquid extraction. In this process, the solution containing the desired constituent must be immiscible; that is, not able to mix; with the rest of the mixture. The process is widely used in extracting oil from oil-bearing materials. PAPER CHROMATOGRAPHY Paper chromatography is defined as a technique used to separate, purify or identify substances by allowing a solvent or solvent system to move over a strip of filter paper or chromatography paper containing these substances. A spot of the mixture to be investigated is placed on the edge of the paper. This point is known as the origin or baseline. Then, the sheet is suspended vertically in a solvent. The spot then rises or moves by capillary action carrying components with it. The components of the investigated spot move at different rates as they absorb differently. After the paper is removed and dried, there is a line of the different components, which also have spots on the line. The components can be identified by the distance they move in a given time. RECRYSTALLIZATION Solids are often pure when first prepared. This is when crystals of a solid are produced, usually from a saturated solution. In crystallization, a definite amount of the substance is dissolved in a specific amount of water in a beaker and is prepared to be heated. The solution is filtered since it is already hot. The insoluble impurities are then separated. Thirdly, the filtered solution is cooled to produce crystals of substances. The now obtained crystals are wet and so are dried by solar heating. EVAPORATION Evaporation is the transition of a liquid to a gaseous form under a temperature lower than its boiling point. The molecules in the water do not have enough heat energy to escape and so, as it gains enough heat, the liquid would turn to vapor. When a significant amount of heat is added to the liquid, it has enough heat energy to quickly phase to a vapor when the liquid’s boiling point is reached. The more energy added, the faster the molecules disperse. As they move this fast, the molecules collide, they take the heat energy they contain and therefore transfer such energy in different amounts. Because of the angle on collision, the transfer can have such an effect that it causes the molecule to escape the liquid as vapor. SUBLIMATION This method of separation is used to separate the solid which converts and reconverts from a solid to a gas from a mixture of solids. When the two compounds are gently heated, one substances collects on the base whilst the other substance, unaffected by heat, remains behind. The bonds are broken between the molecules and so turn the solid to gas and vice versa.