Cause and effect relationships may be used to predict phenomena in natural or designed systems. MS-PS Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed. Science and Engineering Practice 6: Constructing explanations and designing solutions.
The temperature readings for naphthalene. The temperature readings for naphthalene and substance X. The application of freezing point depression is the determination of the molecular weight of the substance X.
A weighed amount of the solute substance X is dissolved in a known mass of solvent naphthalene. The freezing point of the solvent the temperature at which solid and liquid phases are in equilibrium is determined by the cooling of the solution.
When the graph of the time versus temperature was plotted, a longest horizontal portion which is the constant temperature of the graph indicates the freezing of the pure liquid. However, a solution mixture of substance X and naphthalene will freeze over a range of temperature which is lower than the constant freezing point of the solvent naphthalene.
The plot will show a change of slope when solid solvent begins to form. The concentration of dissolved solute will steadily increases as the solvent freezes. This will cause the freezing point to continue decrease after the constant temperature.
Based on the graph plotted for the pure solvent naphthalenethe freezing point obtained is Whereas, the freezing point obtained for solution of substance X and naphthalene is From the results obtained in the experiment, it obeys the theory of freezing point depression stating that the solution which contains naphthalene and substance X will have lower freezing point compared to the freezing point which contains only pure solvent naphthalene.
All the graphs used to determine the freezing point shows a staircase-like shape. For the graph of temperature versus time for naphthalene, initially, the temperature was After that, the temperature continues to fall until the last second the time was recorded.
The shape of this graph did not obtained like a staircase as the initial temperature start to become constant and continue to fall until the end of the experiment. During the starting of the experiment, the temperature of the solvent does not decrease because the solvent was not over heated in the water bath.
Thus, the temperature measured in 0 second is the freezing point of the solvent.
However, the graph for the solution of naphthalene and substance X exhibits a staircase-like shape. The initial temperature was 80oC then there is a slight decrease until it reaches 75oC, the equilibrium state of the substance which is the conversion of liquid to solid state.
After that, the temperature will start to decrease until the end of the experiment. The experimental freezing point was selected based on the temperature that remains the longest period for all the three different solution.
This is because during this period, temperature do not rise until all the solid has melt as heat of fusion is taken up to convert the solid state substance to liquid state. In order to make sure the results obtained obeys the theory, some of the precautions steps should be taken in order to prevent results error.
Firstly, all apparatus used should be washed and rinsed thoroughly with distilled water to avoid contamination occurrence. Furthermore, during the solution is left to melt from solid to liquid, the content should be stirred in order to maintain thermal equilibrium.
Uneven distribution of heat in the solution will caused the temperature obtained not accurate. Thus, the freezing point depression will be affected.
In order to dispose the substances inside the test tube, the substances was melted in the water bath and disposed into the fume chamber. Posted by Goh Kokv at.Experiment 12 – Freezing Point of Solutions A solution freezes at a lower temperature than does the pure solvent.
This phenomenon is called freezing point initiativeblog.com freezing point depression of a solution is a colligative property of the. Lab 7 - Determination of the Molar Mass of an Unknown Solid by Freezing Point Depression Goal and Overview In the first part of the lab, a series of solutions will be made in order to determine the freezing point depression constant, K f, for initiativeblog.com freezing points of these solutions, which will contain known amounts .
Chemistry Experiment 19 Molar Mass Determination y Depression of the Freezing Point Introduction: The most commonly used liquid is water. In this experiment we study the equilibria that can exist between pure water and an aqueous solution, and ice, the solid form of water.
Determining Freezing Points Lab. Determine Freezing Points Lab - Graph. NOTE: Leave the thermometer in the test-tube for the entire experiment. 4) Wait until the liquid in the thermometer has stopped rising. Record this temperature.
Indicate at what point the liquid became a solid. Molecular Mass by Freezing Point Depression Prelab Purpose Graphs Conclusion 1. To determine the molecular mass of an unknown substance by finding the freezing point of two solutions (BHT and para-dichlorobenzene, and BHT and the unknown.
Molecular Mass by Freezing Point Depression Prelab Purpose Graphs Conclusion 1. To determine the molecular mass of an unknown substance by finding the freezing point of two solutions (BHT and para-dichlorobenzene, and BHT and the unknown.
Group 1 Trial 1 The molecular mass of .