Charles’ Law Apparatus, Apparatus

Charles’ Law Apparatus demonstrates the relationship of degree of expansion and temperature.

Jacques Charles, an 18th-century scientist who studied the expansion of heated gases, was the first to make accurate measurements that indicated that the degree of expansion was directly proportional to the increase in temperature. This relationship led scientists to the concept of absolute zero. The high-quality Charles’ Law Apparatus enables students to determine the volume coefficient of expansion of air throughout a temperature range of almost 100°C.

A specially configured glass U tube features one arm with a funnel top and the second arm, graduated, closed at the end and surrounded by a glass water jacket. Concentrated sulfuric acid, placed in the U tube, encloses an arbitrary volume of air and ensures that the air sample is dry. By adding or draining the acid through a stopcock located at the bottom of the U tube, the solution in the tubes can be maintained at even levels while the temperature in the water jacket is varied. Temperature changes when hot water is added through a funnel at the top of the jacket as cooler water is drained through a rubber tube.