Pure Water Graph

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Colligative Properties & Osmotic Pressure

Peter Jeschofnig, Ph.D. Version 42-0149-00-01

Lab RepoRt assistant
This document is not meant to be a substitute for a formal laboratory report. The Lab Report Assistant is simply a summary of the experiment’s questions, diagrams if needed, and data tables that should be addressed in a formal lab report. The intent is to facilitate student’s writing of lab reports by providing this information in an editable file which can be sent to an instructor

obseRvations & QUestions - paRt i
A. Record your observations and your time and temperature data in tables. Use one table for the pure water and one table for the salt solution.

Data Table 1: Pure Water and Salt Solution|
Seconds| Distilled H20Room temp| Distilled H20 Ice bath| SaltwaterRoom temp| Saltwater Ice bath| 0| 25| 19| 24| 12|
30| 24| 13| 23| 8|
60| 23| 11| 22| 5|
90| 22.5| 9| 22| 0|
120| 22.5| 8| 22| 1|
150| 22.5| 6| 22| 1|
180| 22.5| 5| 22| 1|
210| 22.5| 5| | 1|
240| | 5| | 1|
270| | 5| | |
300| | 5| | |
330| | | | |
360| | | | |
390| | | | |
420| | | | |
450| | | | |
480| | | | |
510| | | | |
540| | | | |
570| | | | |
600| | | | |
630| | | | |
660| | | | |

Make two graphs of your data. On one graph plot the data from the pure water. On the other graph plot the data from the salt solution. On both plot temperature on the y-axis and time on the x-axis.

B. Record the freezing point of the pure water and the freezing point of the salt solution. Freezing Point of Salt Sol: 1 degrees Celcius
Freezing Point of Pure H2O: 5 degrees Celcius

C. How do these two freezing points compare?
The freezing point of salt water is lower than the freezing point of pure water.

D. What are some practical applications of freezing point depression, boiling point elevation, and vapor pressure lowering?

There are many practical applications of freezing point depression, boiling point elevation, and vapor pressure lowering. Antifreeze in the radiator of a vehicle is a good practical example of freezing point depression. Antifreeze can assist with the boiling point in the summer months as well as the freezing point in a vehicle in the winter months. Boling point elevation is seen when salt is added to a pot of boiling water. The salt is used to increase the boiling point. Vapor pressure lowering is best seen when we have something that is freeze dried. When an item is freeze dried, the vapor pressures of the pressures are lowered around me. The air around begins to take the heat from the other item and causes it to freeze.

QUestions - paRt ii

A. To what biological structure is the dialysis bag comparable? How is it similar? How is it different? The biological structure that the dialysis bag is mostly comparable to is a cell membrane. Both the dialysis tubing and the cell membrane are highly selective as to what may pass through the membrane. However with an actual cell membrane this is a phospholipid layer that higher concentrations move to lower concentrations. This is the concentration gradient whereas the dialysis tubing is based solely on molecular weight. So as you can see one of these methods is solely mechanical whereas the other is solely chemical.

B. In biological systems if a cell is placed into a salt solution in which the salt concentration in the solution is lower than in the cell, the solution is said to be hypotonic. Water will move from the solution into the cell, causing lysis of the cell. In other words, the cell will expand to the point where it bursts. On the other hand, if a cell is placed into a salt solution in which the salt concentration in the...
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