OBJECTIVES. To successfully separate the substances. To determine the percent of each component in the original mixture.

INTRODUCTION.A mixture is a material system made up of two or more different substances which are mixed but are not combined chemically. A mixture refers to the physical combination of two or more substances on which the identities are retained and are mixed in the form of solutions, suspensions, and colloids.Mixtures are the one product of a mechanical blending or mixing of chemical substances like elements and compounds, without chemical bonding or other chemical change, so that each ingredient substance retains its own chemical properties and makeup. Despite that there are no chemical changes to its constituents, the physical properties of a mixture, such as its melting point, may differ from those of the components. Some mixtures can be separated into their components by physical (mechanical or thermal) means. The 4 main methods of separation discussed in this experiment are extraction, decantation, filtration and recrystalization.Extraction in chemistry is a separation process consisting in the separation of a substance from a matrix. It may refer to Liquid-liquid extraction, and Solid phase extraction. Other techniques include Supercritical carbon dioxide extraction, ultrasonic extraction, heat reflux extraction, microwave-assisted extraction, DIC (instant controlled pressure drop).Extractions use two immiscible phases to separate a solute from one phase into the other. The distribution of a solute between two phases is an equilibrium condition described by partition theory. Boiling tea leaves in water extracts the tannins, the obromine, and caffeine out of the leaves and into the water. More typical lab extractions are of organic compounds out of an aqueous phase and into an organic phase.Decantation is a process for the separation of mixtures, by removing a top layer of liquid from which a precipitate has settled. Usually a small amount of solution must be left in the container, and care must be taken to prevent a small amount of precipitate from flowing with the solution out of the container. It is frequently used to purify a liquid by separating it from a suspension of insoluble particles (e.g. in red wine, where the wine is decanted from the potassium bitartrate crystals). For example, to obtain a sample of clear water from muddy water, muddy water is left in a container until the mud settles, and then the clear water is poured into another container.A mixture of two immiscible liquids can also be separated by decantation. For example, the oil and water extracted from fish may be decanted to obtain the oil. A mixture of kerosene and water can also be separated through decantation.A centrifuge may be useful in successfully decanting a solution. The centrifuge causes the precipitate to be forced to the bottom of the container; if the force is high enough, the precipitate may form a compact solid. Then the liquid can be more easily poured away, as the precipitate will likely remain in its compressed form. A mixture of an insoluble solid in liquid is allowed to stand. The solid is insoluble and settles at the bottom if kept undisturbed for some time. This process is called sedimentation. The clear liquid is then poured off carefully. This process is called decantation.Filtration 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. The fluid that pass through is called a filtrate. Oversize solids in the fluid are retained, but the separation is not complete; solids will be contaminated with some fluid and filtrate will contain fine particles (depending on the pore size and filter thickness). Filtration is also used to describe some biological processes, especially in water treatment and sewage treatment in which undesirable constituents are removed by absorption into a biological film grown on or in the filter medium as in slow sand filtration.There are many different methods of filtration; all aim to attain the separation of substances. Separation is achieved by some form of interaction between the substance or objects to be removed and the filter. The substance that is to pass through the filter must be a fluid, i.e. a liquid or gas. Methods of filtration vary depending on the location of the targeted material, i.e. whether it is dissolved in the fluid phase or suspended as a solid.Finally, recrystallization is a technique used to purify chemicals. By dissolving both impurities and a compound in an appropriate solvent, either the desired compound or impurities can be coaxed out of solution, leaving the other behind. It is named for the crystals often formed when the compound precipitates out.

MATERIALS AND APPARATUS: Sand, benzoic acid, tap water, sodium chloride Beaker, hot plate, filter funnel, stirring rod.

METHODOLOGY:A. EXTRACTION1. Pestle and mortar was used to grind the sample used. This is done in order for us to remove any lumps formed.2. A cleaned 250-ml of beaker was used. The beaker which was used will be labeled as Beaker 1. The mass of the empty beaker was recorded.3. The sample which was grinded using the pestle and mortar was then transferred into Beaker 1. The final mass of the beaker and the sample was recorded. The pestle and mortar used was rinsed with water and dried.4. About 75ml of tap water was then added to the beaker and placed on the hot plate. The mixture was stirred occasionally using a stirring rod. The mixture was then brought to boiling. Once it was boiled, all benzoic acid and sodium chloride should be in solution (No more white solids are visible). If the solids are not completely dissolved about 10ml of water can be added until the dissolution is complete.

B. RECRYSTALLIZATION1. Then, about 100ml of tap water was added into the beaker 1. This supernatant liquid was decanted into a second 250ml of beaker on the hot plate.2. Ice bath was prepared in a 1 L beaker. The 2nd beaker which contained the solutions of benzoic acid and salt was placed into that ice bath. It is ensured that the beaker does not sink into the ice bath.

C. FILTRATION1. The mass of the filter paper was measured.2. The apparatus was assembled for gravity filtration as shown. The filter paper was folded and placed on the filter funnel. An appropriate-sized funnel was selected so the filter paper does not extend over the funnel edge. A beaker was placed below the funnel. The cold recrystallized benzoic acid mixture was poured through the filter funnel. The wet solid was then transferred into the funnel using spatula. 3. The traces of the solids were rinsed into the funnel with small amount of cold water. When the process is complete, the filter paper was removed carefully. The solid crystal was then placed on a watch glass and set aside for drying. 4. The mass of the crystal formed was then measured.

D. DECANTATION:1. To make sure that all the soluble materials are separated from the sand, the sand was washed with about 20ml of boiling water and the washings was decanted into a second beaker. The sand is not allowed to get into the 2nd beaker.2. Beaker 1 containing the sand was warmed, on the hot plate. The sand tends to splatter if heated too rapidly. You may cover the beaker with a watch glass (mass it first!) to minimize losses. When the sand is completely dry, the beaker was allowed to cool to room temperature and mass Beaker 1+sand; record.

RESULTS:RESULTS & CALCULATIONInitial Volume of tap water = 75 mLMaterials

Mass (g)

Sodium Chloride salt (feed)

2.80

Benzoic Acid (feed)

2.80

Sand (feed)

3.70

Mixture of samples

2.80 + 2.80 + 3.70 = 9.30

250 mL Beaker 1 (empty)98.24

Beaker 1 + Mixture of samples98.24 + 9.30 = 107.54

Beaker 1 + Sand 101.66

Sand recovered107.54 - 101.66= 5.88

250 mL Beaker 2 (empty)101.96

Watch glass (empty) 33.70

Watch glass + Filter paper (empty)35.04

Filter paper (empty)35.04 33.70 = 1.34

Watch glass + Filter paper + Crystal36.95

Benzoic Acid recovered36.95-35.04 = 1.91

Beaker 2 + Sodium Chloride 105.77

Sodium Chloride Recovered105.77-101.96 = 3.81

1. Calculating mass fraction of each feed using formula below; Total mass of sample = 9.30 g Mass of Benzoic Acid (feed) = 2.80 g Mass of NaCl salts (feed) = 2.80 g Mass of Sand (feed) = 3.70 g

i) Mass Fraction of Benzoic Acid = = 0.301

ii) Mass Fraction of NaCl salt = = 0.301

iii) Mass Fraction of Sand = = 0.398

2. Calculating mass fraction for each recovered samples;

Using formula:

Mass of Sand recovered = 3.42 g Mass of Benzoic Acid recovered = 1.91 g Mass of NaCl recovered = 2.61 g Total recovered mass (mixture sample) = 3.42 g + 1.91 g + 2.61 g = 7.94 g

i) Mass Fraction of NaCl salt = = 0.329

ii) Mass Fraction of Benzoic Acid = = 0.241

iii) Mass Fraction of Sand = = 0.430

3. Calculating the percent mass of each samples in the mixture;

i) Benzoic Acid = 0.301 X 100% = 30.1 %ii) NaCl salt = 0.301 X 100% = 30.1 %iii) Sand = 0.398 X 100% = 39.8 %

4. Calculating percent error based on experiment;

Using formula: % error = x 100%

i) % error Benzoic Acid = x 100% = 32.1 %

ii) % error NaCl salt = x 100% = 6.79 %

iii) % error Sand = x 100% = 7.57 %

iv) Total % error = x 100% = 14.62 %

DISCUSSION: Based on this experiment, we have learnt many types of separations of a solid mixture. Here, extraction, re-crystallisation, filtration and decantation were studied using mixture sample which consist of benzoic acid, sodium chloride salt (NaCl) and also sand. Initially, the mass of each samples were weighed using electronic balance. The mass of benzoic acid weigh was 2.80 g, sodium chloride (NaCl) salt weighing 2.80 g and 3.70 g for sand. All the results were recorded as shown is the above Table 1. Furthermore, from the values tabulated above, percentage of mass of each sample was calculated. The calculation was illustrated above. It is determined that, percentage of mass for benzoic acid was 30.1%, followed by sodium chloride (NaCl) with percentage of mass 30.1% and also 39.8% for sand fed. In spite of that, the percentage error for each samples were also calculated after recovery of each samples. In order to calculate the percentage error of each samples, the mass fraction for each samples fed and also recovered was taken into considerations. From the calculation above, the mass fraction of feed samples (Benzoic Acid, NaCl and Sand) are 0.301, 0.301 and 0.398 respectively. Besides that, the mass fraction of the recovered samples are 0.241 (Benzoic Acid), 0.329 (Sodium Chloride) and 0.430 (sand). Next, the percentage of error of each samples and the total error was found. Here, benzoic acid has percentage of error of 32.1%, percentage of error of 6.79 % for sodium chloride (NaCl) salt and 7.57 % for sand. The total percentage of error determined was 14.62%. Hence, from this experiment, it is clearly explained that there are many types of separation method that can be used to separate a solid mixture. Moreover, the errors occurred in this experiment could be minimised by repeating this experiment at least thrice to achieve accuracy. Also, the objectives of this experiment were achieved.

LIMITATIONS AND PRECAUTIONARY STEPS:1. There might be some solutes left in the beaker while pouring out the solution into the filter funnel. This may affect the final crystals formed at the end of the experiment. Therefore, the solution was mixed evenly before pouring the solution.2. Wash the beaker before using it. Any impurities inside the beaker may affect the mass of the final crystals.3. While performing decantation, the solution is poured out slowly because if the solution is poured out rapidly, this may cause the solids at the bottom of the beaker to be removed accidentally from the beaker.

CONCLUSION.There are numerous methods that can be used to separate a mixture. The main method that was discussed and used in this experiment was filtration. In conclusion, we managed to successfully separate the substances and determine the percent of each component in the original mixture. It can therefore be said that the objectives of this experiment were met and achieved and therefore this experiment was a success.

REFERENCES.1. Separating Mixture. http://www.bbc.co.uk/bitesize/ks3/science/chemical_material_behaviour/compounds_mixtures[Accessed on 10th June 2015]

2. Separation Processes.