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NATALIE KOH 210

This is my SCIENCE LAB BOOK to record the detailed findings and the process as i conduct this project

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Friday, July 22, 2011

FINAL PROPOSAL

Topic of investigation : How different impurities affect the rate of evaporation.

A Observations made
Singapore is a country with a lack of natural resources, especially drinking water. The imported water contract with Malaysia will end very soon and Singapore needs to find alternative methods to obtain fresh water. One of these methods is desalination. In this process, seawater is evaporated and the water vapour which condenses forms pure water safe for drinking. So, I was wondering how different impurities in seawater will affect the evaporation rate. Hence, I will be testing salt solution and water with sand, which is insoluble and also I would like to test how different soluble impurities will affect the evaporation rate, so I have decided to include a sugar solution, as well as set up a control experiment of plain water. These will be left to evaporate and then the evaporation rate can be calculated and be compared.


B Research Question
How do different impurities in water affect the evaporation rate?


C Hypothesis statement
My hypothesis is that the water with sand will evaporate at the same rate as plain water, then the salt solution and finally the sugar solution.

D A short summary of research done on the area of investigation
The reason why impurities affect the rate of evaporation is because of vapour pressure. Water evaporates because of the pressure of the vapour from the evaporation of the liquid, so the liquid needs to evaporate to attain equilibrium pressure. The presence of non-volatile impurities will lower the vapour pressure, so the liquid can evaporate less to attain equilibrium pressure. The reason why the salt solution evaporates faster than the sugar solution is because of their molecular weight. Sugar has a higher molecular weight, so even though the same amount of salt and sugar are dissolved in water, there is actually more impurities in the sugar solution. Hence, the vapour pressure is lowered even more, and the evaporation rate is lower. Finally, the reason why water with sand will evaporate at the same rate as plain water is because insoluble liquids will not affect the evaporation rate.


discovery @ 8:44 AM