If the molecule's position lies in the range between r and r+dr (i.e. , if its x coordinate lies between x and dx , its y coordinate between y and y+dy , and its z coordinate between z and z+dz) and if its momentum lies in the range between p and p+dp (i.e. , if its x component of momentum lies between px and px+dpx) , then the volume of phase space corresponding to this range of r and p is