a. If the student did not stir the mixture before decanting the water the percentage of sand would be unaffected. Though the percent of salt would be higher because the salt did not have the opportunity to dissolve.
b. Again the percentage of sand would be unaffected, if a student added additional water to the beaker. The amount of sand, would remain consistent if the student properly stirred/decanted the mixture; only the water containing salt would be effected.
c. If the beaker was not heated for the second time, there is a small margin for error. Heating the beaker and sand for a second time is to ensure that the sand is completely dry. If this action was not performed then the sand may not be completely dried and this will cause the percent of sand to be higher due to the presence of water and the shortened drying process.
2. At the end of the experiment, it was determined that the mixture was heterogeneous. The mixture was determined to be heterogeneous based on the fact that the mixture can be separated.
3. In an experiment to separate a mixture of sand, lead chloride and sodium nitrate. I would attempt to separate the sodium nitrate first because it is soluble in cold water, and would not interfere with the lead chloride because it is only soluble in hot water. After the sodium nitrate is separated then the lead chloride. Lead chloride is soluble in hot water. I chose to separate the mixture this way because sand is an insoluble substance in both hot and cold water.