when there is a change in phase and the change can be reversed

mass per unit volume

the smallest part of an element that still retains the same properties of the element

the building blocks of all matter

when there is a change in phase and the change cannot be reversed

composed of molecules that move freely among themselves but do not tend to separate like those of gases

composed of molecules that move at high speeds and take the shape of the container; vibrate more freely at higher speeds

the temperature at which a solid turns into a liquid; it is equal to the freezing point

the temperature at which a liquid changes to a vapor or gas

the ability of a substance to dissolve

composed of molecules that are compacted together and do not move

something that has mass and occupies space

the amount of matter a substance contains