Why are two changes of state of the refrigerant necessary to operate a refrigerator?

Ahypothrticalax type of ceramic material is known to have a density of 2.10 g/cm3 and a unit cell of cubic symmetry with a cell edge length of 0.57 nm. the atomic weights of the a and x elements are 28.5and 30.0 g/mol, respectively. on the basis of this information, which of the following crystal structures is (are) possible for this material: sodium chloride, cesium chloride, or zinc blende

Which position represents spring in the southern hemisphere? a) b) c) d)

Many pharmaceutical drugs are organic compounds that were originally synthesized in the laboratory. which two scientific disciplines are bridged by pharmaceutical drugs? chemistry and forensics chemistry and medicine biology and forensics biology and criminology