Ultrasonic

a term used to describe sound waves that are inaudible to humans as they have a frequency above 20kHz. Although the human ear is incapable of detecting such a high FREQUENCY, some animals, such as dogs and bats, can detect ultrasonic waves (also known as ultrasound). Ultrasound is used wisely in industry, medicine and research. For example, it is used to detect faults or cracks in underground pipes and to destroy kidney stones and gallstones. The most recent development in ultrasonics is their use in chemical processes to trigger reactions involved in the production of food, plastics and antibiotics. Ultrasonics make certain chemical processes safer and cheaper as they eliminate the need for high temperatures and expensive catalysts.

Taken from Dictionary of Science

Labile

a term used in chemistry which means not stable, likely to change.

Taken from Dictionary of Science

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The term is used to describe a relatively unstable and transient chemical species. As a general example, if molecule exists in a particular conformation for a short life-time, before adopting a lower energy conformation, the former molecular structure is said to have 'high lability' (such as C₂₅, a 25-carbon fullerene spheroid). The term is sometimes also used in reference to reactivity - for example, a complex which quickly reaches equilibrium in solution is said to be labile (with respect to that solution).

Taken from Wikipedia