How can understanding change of state you to seprate a salt water solution

You can apply the fact that water changes from liquid to gas when heated to its boiling point.

Explanation:

Salt solution contains salt dissolved in water. The water can be separated from the salt by evaporation of the solution to dryness. This exploits the fact that water changes from liquid to gas at it's boiling point. This is an example of change of state. When heated strongly, all the water present will be converted to vapour and the solid salt reappears.

answers: to make sure that all of the broken pieces of tablet were added to the water, to allow for fair comparison of all three trials, with different particle sizes to avoid experimental error