Download Physics and Chemistry 3º ESO Techniques to separate the

Physics and Chemistry 3º ESO
Techniques to separate the components of a mixture
1. - Introduction:
In this lab, we will see how we can separate the components of mixtures. Depending
on the components and the nature of the mixture (homogeneous or heterogeneous) we
can use different techniques:
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Decantation
Filtration
Magnetic separation
Crystallization
Distillation
2. - Theoretical basis:
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Decantation:
It is a process for the separation of heterogeneous mixtures formed by
two immiscible liquids with different densities. A mixture of kerosene and water can be
separated through decantation.
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Filtration:
It is commonly the mechanical or physical operation which is used for the separation of
solids from fluids (liquids or gases) by interposing a medium through which only the
fluid can pass.
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Magnetic separation:
It is the process of separating magnetic substances from the non-magnetic substances
in a mixture with the help of a magnet.
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Crystallization:
It is a technique which chemists use to purify solid compounds in homogeneous
mixtures. It is based on the principles of solubility: compounds (solutes) tend to be
more soluble in hot liquids (solvents) than they are in cold liquids. If a saturated hot
solution is allowed to cool, the solute is no longer soluble in the solvent and forms
crystals of pure compound. Impurities are excluded from the growing crystals and the
pure solid crystals can be separated from the dissolved impurities by filtration.
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Distillation:
Distillation is a widely used method for separating mixtures based on differences in the
conditions required to change the phase of components of the mixture. To separate a
mixture of liquids, the liquid can be heated to force components, which have different
boiling points, into the gas phase. The gas is then condensed back into liquid form and
collected. Repeating the process on the collected liquid to improve the purity of the
product is called double distillation. Although the term is most commonly applied to
Physics and Chemistry 3º ESO
Techniques to separate the components of a mixture
liquids, the reverse process can be used to separate gases by liquefying components
using changes in temperature and/or pressure.
Distillation is used for many commercial processes, such as production of gasoline,
distilled water, xylene, alcohol, paraffin, kerosene, and many other liquids. Types of
distillation include simple distillation (described here), fractional distillation (different
volatile 'fractions' are collected as they are produced), and destructive distillation
(usually, a material is heated so that it decomposes into compounds for collection).
3. – Tasks:
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Decantation: Separating a mixture of oil and water.
Material: Separating funnel, graduated flask or beaker, water and oil.
Experimental procedure: Introduce a mixture of water and oil in a separating funnel.
Close it and shake it. Let stand and opens the top. Subsequently using the funnel´s
key the portion of water is removed staying the portion of oil inside the funnel.
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Filtration: Filtration of a mixture of sand and water.
Material: Watchglass, graduated flask, filters paper, sand and water.
Experimental procedure: Place a filter in the funnel according to the following
illustration:
Physics and Chemistry 3º ESO
Techniques to separate the components of a mixture
Then pour the mixture of sand and water gradually into the funnel across the filter.
Sand will remain separated into the filter but water will pass across to the flask.
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Magnetic Separation: Separation of a mixture of salt and iron filings.
Material: Magnet, watchglass, salt, iron fillings
Experimental procedure: Place a mixture of salt and iron fillings in a watchglass;
and then place a magnet into the mixture; the iron filings will be attracted by the
magnet and both components will be separated to each other.
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Crystallization: Separation of salted solutions
Material: Crystallizer, graduated flask, beaker, Bunsen burner or a stove.
Experimental procedure: When lead nitrate reacts with potassium iodide then a
golden yellow precipitate of lead iodide is formed. When the precipitate is
heated (70ºC) then cooled, placed in a crystallizer and dried, attractive shiny
golden rays will illuminate its sides. It will appear as rainy golden shower.
A chemical reaction has happened: Pb(NO3)2 + 2 KI ------- PbI2 ! + 2 KNO3
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Distillation of wine:
Experimental Procedure: In this procedure, wine will be distilled and the
alcoholic content of the distillate determined. The distillate from wine is called
brandy (short for Brandywine).
Physics and Chemistry 3º ESO
Techniques to separate the components of a mixture
1. Obtain a thermometer distilling flask and condenser from the front of the
room.
2. Assemble the distilling apparatus as shown in the figure (See next page).
3. Remove the thermometer and place a boiling chip and about 75ml of wine
using a long-stem funnel into the distilling flask.
4. Turn on the cooling water and have the instructor check your setup, then
apply the heat to the wine. After boiling begins, reduce the heat so the wine
boils at a moderate rate.
5. Watch the temperature closely while distilling and collect the distillate coming
from the condenser while the temperature is in the range 80-85ºC. The
temperature should remain nearly constant in this range.
6. When the temperature rises above 85ºC, begins to increase, quickly change
collecting flasks then continues distilling until the temperature is between 98
and 100ºC
7. Record the temperature range over which you collected the alcohol enriched
distillate.