Today is 6 March 2009 -- . This note is about the salt dissolving experiment

The experiment was to see if a change in dissolving time occurred as more and more salt entered the solution.  This is one aspect of solution chemistry.  Three different water temperatures were studied; cold, room temperature and hot.  Students added about 7 grams of table salt, sodium chloride or NaCl,  to 100 ml of water, stirred until it dissolved and timed how long it took.  They weighed the container of water before and after.  The difference in weight was how much salt they had added.  Then they repeated this with another approximately 7 grams, stirred, timed and weighed.  They repeated it a third time.  The results were to be graphed as the total weight of salt on one axis and the dissolving time for each salt addition on the the other axis.  For example, let us say the first 7 grams took 50 seconds to dissolve, the second 7 grams took 62 seconds and the third took 72 seconds.  The student would make marks at the intersection of 7 g and 50 sec,  14 g (7g +7g) and 62 seconds and 21 g (7g + 7g + 7g) and 72 seconds.  This example shows that as more salt is added to the solution, it takes longer to dissolve.  What would it mean if less time was taken?  

Some students used three different temperatures of water and attempted to plot that data.  That was incorrect and the data was worthless.  They were to use the same water temperature; either cold, hot or room temperature, and add salt to it.  By comparing data between different groups of students, testing at different temperatures, the class was supposed to determine if hot water dissolved the salt the fastest and cold water the slowest, or some other way.