How does reverse osmosis function?

Reverse osmosis operates by applying mechanical pressure to force water through a semipermeable membrane. This membrane allows certain molecules, specifically water, to pass through while blocking larger particles, contaminants, and impurities. The process is driven by the difference in osmotic pressure; when pressure is applied to the side with the higher concentration of solutes (contaminated water), it overcomes the natural osmotic movement, effectively purifying the water as it passes to the side with lower solute concentration.

This method is particularly effective in desalinating seawater and removing various dissolved solids from drinking water. Reverse osmosis is widely used in both industrial applications and home water purification systems due to its efficiency in producing clean, safe drinking water.

The other methods mentioned in the choices do not describe the functioning of reverse osmosis. Evaporation uses heat, chemical reactions focus on altering water chemistry rather than physically filtering it, and sand and gravel filtration typically relies on gravity and larger particle filtration rather than the specific mechanism of pressure-driven membrane separation.