You are worried that a solid substance has dissolved in a beaker of water in a lab. What would be a way to separate the substance from the water?

Question

Pass the solution through a filter to let the dissolved substance separate.
Boil the water away, leaving the substance behind in the beaker.
Use a magnet to draw out the solid substance from the water.
Pour the liquid along a rough surface that would catch the solid particles but not the water.

Answer 1

To separate a solid substance that has dissolved in water, the best method from the options provided would be to boil the water away, leaving the substance behind in the beaker. This method is effective because once the water evaporates, any dissolved solids (if they crystallize or remain in solid form after the water is removed) will remain in the beaker.

The other options are not appropriate:

• Passing the solution through a filter would work if the solid is suspended but not if it has dissolved completely, as dissolved substances cannot be separated by filtration.
• Using a magnet would only be effective if the substance is magnetic, which is unlikely for common dissolved solids.
• Pouring the liquid along a rough surface wouldn't effectively separate a dissolved solid from water.

Therefore, boiling the water is the most suitable method to separate the dissolved solid from the solution.