In terms of particles arrangements, why does the entropy of water decreases when the water freezes

Matter- occupies space and possesses rest massno matter is the opposite

Ido not understand. 

It is a mixture. simply put, a compound must be pure, that is, of only one chemical structure and composition. a mixture is made of different chemical substances (i.e. elements, molecules, compounds) that are not chemically bonded to each other, but instead physically grouped together, as in the case of gasoline (a homogeneous solution).