Question

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1. why is the salt solution heated in step 6?
2. how might the final traces (small amounts) of water be removed from your sand samples to ensure that they are totally dry?
3. give two reasons why the sand you have obtained might still be contaminated with salt.

Explanation:

1. Heating the salt - solution is usually to evaporate the solvent (water) and obtain salt crystals. Evaporation is a common separation technique in chemistry for separating a solute from a solution.
2. To remove the final traces of water from sand samples, one could use a desiccant (a substance that absorbs moisture) or heat the sand in an oven at a controlled temperature for a longer time. The heat will cause the water to evaporate, and the desiccant will absorb any remaining moisture.
3. The sand might still be contaminated with salt if the salt - water solution was not completely filtered off before drying, leaving some salt on the surface of the sand grains. Also, if the evaporation of the salt - water solution was not complete, some salt - laden water could have re - deposited salt on the sand during the drying process.

Answer:

1. To evaporate the solvent (water) and obtain salt crystals.
2. Use a desiccant or heat in an oven at a controlled temperature for a longer time.
3. Incomplete filtration of salt - water solution; Incomplete evaporation and re - deposition of salt - water.