How does filtration separate a mixture of sand and water?

• A. By boiling the mixture until the sand settles.
• B. By shaking until sand dissolves.
• C. By passing the mixture through a filter that traps the solid sand while letting the water through.
• D. By evaporating water and leaving sand behind.

Answer: (C)

Filtration works by using a barrier with tiny holes to separate a mixture. When you pour the sand–water mixture through a filter, the water can flow through the filter, but the sand grains are too large to pass, so they get trapped on the filter. Since sand doesn’t dissolve in water, you end up with clean liquid passing through and solid sand left behind. Other methods don’t fit because boiling would remove water as vapor rather than separate via a barrier, evaporation would leave the sand after the water is removed, and shaking won’t dissolve the sand since it’s insoluble.