Aphysical property is one that
cannot be observed
can be observed by altering the identity
can be changed without altering the identity of a substance
must be observed through chemical means

Asubstance is held in an open container. its particles move past one another at random speeds but do not leave the container. heat is removed from the system, and the particles slow down. when enough heat is removed, the particles no longer have enough speed to overcome the weak attractive forces between them. when this happens, the substance enters its solid state. the process described above is known as .