Sonochemistry

Power ultrasound in the 20-100 kHz range is used in chemistry. The ultrasound does not interact directly with molecules to induce the chemical change, as its typical wavelength (in the millimeter range) is too long compared to the molecules. Instead:

• It causes cavitation which causes local extremes of temperature and pressure in the liquid where the reaction happens.
• It breaks up solids and removes passivating layers of inert material to give a larger surface area for the reaction to occur over.

Both of these make the reaction faster.