Cyclohexane Melting & Freezing

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1 Cyclohexane Melting & Freezing Sambavan Jeyakumar & Archie Woodhouse Aim The aim of the experiment was to find the melting point and freezing point of cyclohexane and observe what happened to the cyclohexane as heat was applied and decreased and the changes of the molecules in the chemical Apparatus Retaught Stand Clamp x 2 Boss Head x 2 Test Tube Beaker x 3 Crushed Ice Laptop with Logger Pro Data Logger Spatula/Stirring Rod Salt (NACl) Cyclohexane (C 6 H 12 ) Water (H 2 0) Measuring Cylinder Method 1. Add approximately 15mL cyclohexane into a test tube using via a measuring cylinder 2. Carefully clamp the test tube in a vertical position 3. Start the Logger Pro as you place the Data Logger into the cyclohexane 4. Lower the test tube into a beaker containing crushed ice and slowly stir the ice with either the spatula or the stirring rod 5. When the temperature reaches 10 o C, replace the crushed ice beaker with another beaker with crushed ice and common salt (4 spatula full) Continue recording until the temperature reaches about -5 o C 6. Replace the ice-salt beaker with cold water filled beaker. This will be hotter so it will start to melt 7. Continue recording the temperature as it rises. Try to let it reach 10 o C and 15 o C 8. observe what occurs as it changes state over time

2 Here is the graph and the table of results TIME (SEC) 0 TEMP ( C)

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4 Discussion/Results Conclusion Melting Point: 5 o C Freezing Point: 6 o C As when heat was decreased the cyclohexane dropped down rapidly but slowed down when changing states of matter. When salt was added to the freezing ice the temperature dropped even more and went past 0 into the negative temperatures. As heat was added it rose gradually because after being in such a cold state it took it a while to heat up again. It steadily increased and started to plateau out once it reached 5 o C to 6 o C as it was changing state back to liquid. When it reached about 10 o C we turned off the Data Logger Pro so we couldn t see what happened after. When we changed cooling and warming mediums, the graph showed significant decreases and increases in temperature. When the cyclohexane was changing states of matter the graph showed that it stayed almost the exact same temperature until it had transformed. When heat was added the temperature the cyclohexane rose slowly but surely. This was because the cyclohexane was just placed in polar like temperatures it took a while for it to adjust to the warmer water. There were two plateaus in our graph. One was near the beginning at around 5 o C and the other was near the end around 6 o C. The first one plateaued for 300 seconds and was almost the exact same temperature the whole way through. This was because at this certain time there was a change of state and because of this transformation the cyclohexane didn t cool at all as it was snap-freezing and in a couple of seconds it was solid. The other time was when it was rising again and it reached its

5 melting point it changed state again and the cyclohexane didn t show significant change but instead it unfroze and most of it melted. As, notified before the melting point was 5 o C and the freezing point was almost 5 o C as well. We can identity this on the graph as the temperature started to plateau out and change state. It started to plateau out because it snap-froze and melted in a matter of seconds and it didn t change the temperature of the cyclohexane until it had changed state. When the cyclohexane reached 5 C we added salt to the Ice slurry this then made the ice go down to minus five C. The reason this happens is that the salt is not actually making the ice colder. The internal portions of the ice are already below 0 degrees Celsius. The salt, or NACl, gets in the way of the intermolecular forces of the water, allowing the ice to melt at lower temperatures and remain in the water phase below 0. In other words, the water molecules are normally rigid enough to freeze at 0 degrees, but the addition of salt makes it more difficult for them to be rigid enough. This lowers the melting point.