Transiton+Temeperature+of+Sodium+Thiosulphate+Pentahydrate

** __Introduction__ **
toc When substances change from one solid phase into another the change is accompanied by absorption or release of heat. The temperature at which such a change takes place is called the transition temperature. This change can be thought of as a change from one compound to another. In this experiment, the compound used is Sodium Thiosulphate Penta Hydrate (Na2S2O3∙5H20). Hydrates are formed when ionic compounds are formed in water and then isolated as solids, therefore the water remains trapped in the compound. Hydrates are written with a dot between the ionic compound and the amount of water molecules involved with the compound. This indicates the number of water molecules per one molecule of the ionic compound. Though water is involved in the chemical formula, this does not indicate that the substance is wet. In fact, many hydrates have dry appearance and touch. When water is removed from the hydrates, one is left with the anhydrous compound (dehydrate). When these hydrates are heated (change in temperature), the water will evaporate and thus the compounds will no longer be hydrates. When water vapour is added to the dehydrates, the dehydrates absorb the water vapour to form a hydrate.

In this experiment, an attempt will be made to find the transition temperature of a specific compound: Sodium Thiosulphate Penta Hydrate (Na2S2O3∙5H20).

A variety of methods can be used to determine the transition temperatures of salt hydrates. The basis of the method used in this experiment is that the temperature will rise constantly until the hydrate evaporates, thus changing state. Thus, on heating crystals of Na2S2O3. H2O, the temperature should rise normally until the hydrate begins to change into an anhydrous salt (i.e. water evaporates). Then the temperature remains constant until the transformation is complete. If the reverse change is allowed to take place, there is an evolution of heat. The temperature will fall at a definite rate until the transition point is reached. Then the temperature stays constant until all of the substance has been transformed. Therefore, by plotting a time vs. temperature curve, the transition point can be determined. When cooling the hot solution in an undisturbed manner, super cooling usually occurs below the transition point, and after falling 4 or 5 degrees C, the temperature of the compound suddenly rises causing crystallization, thereby providing an accurate transition point. For this experiment, the compound will be placed in a test tube, which in turn will be placed in a large beaker filled with water. An air jacket (a container placed on top of test tube to prevent outside air flow) will be used while cooling the compound. A single crystal of Sodium Thiosulphate Penta Hydrate (Na2S2O3∙5H20) will be added, and will act as a seed crystal. Seed crystals are used to expedite the crystallization of the compound as they eliminate the need for random molecular collision/interaction. By introducing an already pre-formed basis of the target crystal to act upon, the intermolecular interactions are formed much more easily than relying on random flow.

**__Materials__**

 * Retort stand
 * Ri ng clamp
 * Wire gauze
 * Bunsen burner
 * Flint lighter
 * Beaker tongs
 * Thermometer
 * Boiling tube
 * 20 mL of Sodium Thiosulphate Pentahydrate
 * Electronic scale
 * 150 mL of water
 * Temperature Probe
 * Computer
 * Scoopula
 * 1 L beaker
 * Safety goggles

** __Procedure__ **
1) Wear safety goggles 2) Set up a retort stand and clamp a ring clamp 30 cm above the base. 3) Set up a temperature probe attatched to a computer 4) Place a piece of wire gauze on the ring clamp so that the wire gauze fully covers the clamp. 5) Place a Bunsen burner beneath the clamp. 6) Place 100 mL of water into a 250 mL beaker and place the beaker onto the wire gauze until stable 7) Place a sensitive thermometer along with a temperature probe into the boiling tube 8) Place 50 mL of Sodium Thiosulphate Pentahydrate into a boiling tube 9) Place the boiling tube into the beaker 11) Record the compund's physical properties of weight, colour and other noticeable observations at the certain temperature. Mass will be measure with the use of an electronic scale 12) Ignite the Bunsen burner with a flint lighter and adjust to a moderate flame. 13) Start recording data with use of the temperature probe 14) When the substance melts, carefully remove the boiling tube using boiling tube clamps and place it into an air jacket 15) When the temperature drops to 40 degrees C, add one crystal of sodium thiosulphate pentahydrate and stir carefully 16) The temperature will increase suddenly and once the temperature remains constant, stop the recording of the data 17) Empty the contents of the beaker safely and wash the beaker.

** __Observations__ **
The following table displays the relationship between time and temperature of sodium triosulphate pentaphydrate over the period of 30 minutes – 0 to 1800 seconds. The time is shown at 30 second intervals. The table also displays the occurring procedural steps. Data in blue is mathematically approximated. __Relationship Between Time (s) and Temperature **(**** ˚C) Between 0s and 1800s **__ For a greater understanding, below is a table displaying the temperature, recorded at 30 second intervals, of sodium thiosulphate pentahydrate after the heat was turned off. At time 331, the heat was turned off and the boiling tube was placed in an air jacket. Once the temperature reached 40˚C, one crystal of sodium thiosulpahte pentahydrate was added.
 * ** Time (s) ** || ** Temperature (˚C) ** || ** Procedural Step ** ||
 * 0 ||  21.1  ||  Initial Temperature  ||
 * 30 ||  20.9  ||   ||
 * 60 ||  21.9  ||   ||
 * 90 ||  24.5  ||   ||
 * 120 ||  29.9  ||   ||
 * 150 ||  44.7  ||   ||
 * 180 ||  50  ||   ||
 * 210 ||  55.9  ||   ||
 * 240 ||  68.6  ||   ||
 * 270 ||  67  ||   ||
 * 300 ||  73  ||  At 294s, all of the substance has become liquid. Substance is let to heat for to an additional 5˚C  ||
 * 330 ||  65.6  ||  Temperature peaks at 73.8˚C having risen another 5˚C. Heat is turned off. Boiling tube is placed in an air jacket. Substance begins to cool.  ||
 * 360 ||  64.3  ||   ||
 * 390 ||  64.8  ||   ||
 * 420 ||  63.3  ||   ||
 * 450 ||  62.4  ||   ||
 * 480 ||  61  ||   ||
 * 510 ||  60.1  ||   ||
 * 540 ||  58.4  ||   ||
 * 570 ||  56.8  ||   ||
 * 600 ||  56.2  ||   ||
 * 630 ||  55.3  ||   ||
 * 660 ||  54.7  ||   ||
 * 690 ||  53.8  ||   ||
 * 720 ||  53.1  ||   ||
 * 750 ||  52.2  ||   ||
 * 780 ||  51.4  ||   ||
 * 810 ||  50.8  ||   ||
 * 840 ||  50  ||   ||
 * 870 ||  49  ||   ||
 * 900 ||  48.2  ||   ||
 * 930 ||  47.5  ||   ||
 * 960 ||  46.8  ||   ||
 * 990 ||  46  ||   ||
 * 1020 ||  45.5  ||   ||
 * 1050 ||  45  ||   ||
 * 1080 ||  44.2  ||   ||
 * 1110 ||  43.5  ||   ||
 * 1140 ||  43.1  ||   ||
 * 1170 ||  42.4  ||   ||
 * 1200 ||  41.8  ||   ||
 * 1230 ||  41.1  ||   ||
 * 1260 ||  40.8  ||   ||
 * 1290 ||  40.3  ||  The substance reaches 40˚C at 1294s. One crystal of sodium thiosulpahte pentahydrate is added to the boiling tube  ||
 * 1320 ||  42.7  ||   ||
 * 1350 ||  47.2  ||  As the temperature begins to stabilize, 47.6˚C is the transition temperature.  ||
 * 1380 ||  47.9  ||   ||
 * 1410 ||  48.2  ||   ||
 * 1440 ||  47.9  ||   ||
 * 1470 ||  47.9  ||   ||
 * 1500 ||  47.8  ||   ||
 * 1530 ||  47.7  ||   ||
 * 1560 ||  47.7  ||   ||
 * 1590 ||  47.6  ||   ||
 * 1620 ||  47.8  ||   ||
 * 1650 ||  47.6  ||   ||
 * 1680 ||  47.8  ||   ||
 * 1710 ||  47.7  ||   ||
 * 1740 ||  47.6  ||   ||
 * 1770 ||  47.6  ||   ||
 * 1800 ||  47.6  ||   ||

__Relationship Between Time (s) and Temperature ** ( **** ˚C) After Heat Was Turned Off (311s - 1781s) **__


 * Time (s) ||  Temperature (˚C)  ||
 * 311 ||  73.8  ||
 * 341 ||  65.1  ||
 * 371 ||  63.7  ||
 * 401 ||  64.2  ||
 * 431 ||  63.1  ||
 * 461 ||  61.9  ||
 * 491 ||  60.6  ||
 * 521 ||  59.5  ||
 * 551 ||  57.7  ||
 * 581 ||  56.5  ||
 * 611 ||  55.7  ||
 * 641 ||  55.1  ||
 * 671 ||  54.4  ||
 * 701 ||  53.5  ||
 * 731 ||  52.7  ||
 * 761 ||  51.8  ||
 * 791 ||  51.1  ||
 * 821 ||  50.2  ||
 * 851 ||  49.5  ||
 * 881 ||  48.7  ||
 * 911 ||  47.9  ||
 * 941 ||  47  ||
 * 971 ||  46.6  ||
 * 1001 ||  46  ||
 * 1031 ||  45.1  ||
 * 1061 ||  44.7  ||
 * 1091 ||  43.9  ||
 * 1121 ||  43.6  ||
 * 1151 ||  42.8  ||
 * 1181 ||  42.1  ||
 * 1211 ||  41.6  ||
 * 1241 ||  41.1  ||
 * 1271 ||  40.7  ||
 * 1301 ||  40  ||
 * 1331 ||  44.3  ||
 * 1361 ||  47.7  ||
 * 1391 ||  48.1  ||
 * 1421 ||  47.9  ||
 * 1451 ||  48.1  ||
 * 1481 ||  47.9  ||
 * 1511 ||  47.9  ||
 * 1541 ||  47.9  ||
 * 1571 ||  47.8  ||
 * 1601 ||  47.8  ||
 * 1631 ||  47.8  ||
 * 1661 ||  47.8  ||
 * 1691 ||  47.6  ||
 * 1721 ||  47.6  ||
 * 1751 ||  47.6  ||
 * 1781 ||  47.7  ||

**__Calculations__**
Below is the plotted graph displaying the visual relationship between time (s) and temperature (˚C). The full duration of the experiment is shown.  

The following graph visually represents the relationship between time and temperature during the time period of 311s-1781s at intervals of 30 s. During this time period, the heat is turned off at 311s and a crystal is added at 1294 s.



** __Discussion__ **
1) What is the significance of adding one crystal of Sodium Thiosulphate Pentahydrate at the end?

The single crystal of sodium thiosulphate acts as a seed crystal and speeds up the crystallization process. (add on)


 * 2) Judging from the experiment, what information does the transition temperature of a compound provide?**


 * 3) Was this reaction endothermic or exothermic? How do you know?**


 * 4) What are some practical uses of transition temperature?**

**Sources of Error**
In determining the transition temperature of hydrates such as sodium thiosulphate pentahydrate, knowledge of experimental errors are important, they can lead to inaccurate results. Sources of experimental include faulty equipment such as the temperature probes. The results from the experiment were staggered due to the capabilities of the program "Logger PRO" which only allowed five minute time allocations and in result, approximately 29 seconds between each time interval was lost. There was some infromation lost in the transportation time in transferring the boiling tube from the clamp into the air jacket. Since the test tube was heated, it was slowly handled with caution. The lost information was obtained by simple mathematical calculations and averaged on the trends. Due to human error, there was no way to tell accurately when the sodium thiosulphate pentahydrate has tranformed fully into a liquified state. It was judged by vision and it could have been incorrect. Contamination could have occured in any of the materials used in the experiment such as the beakers, the scoopula, or the sodium thiosulphate pentahydrate.

we didn't take note of the temperature cause we used a computer we used a temperature probe yes. we did wait an extra 5 degrees i made a mistake on the excel sheet explain what the air jacket is 200 OR 150 ml of water i need to check we used a 250 mL beaker.... observations/data/calculations (I'm doing this part. DID YOU KNOW WE HAVE 30 MINUTES OF DATA?) error (some i thought of) the computer program could only have graphs up to five minutes so there was a lag between each graph approx 29 seconds each...as a result those results we obtained through simple math and averages.... time lag of transferring to air jacker hard to deteremine if all of the sodium thiosulpahte had liquified (this might be human. hm unsure) thermoter only had to .1 decimal. not very accurate.

okay...here are links to our data.