Matter is anything that has mass and takes up space (volume). How does volume change as matter changes state? A. The density of matter remains the same, only energy of the atoms changes.

B. matter becomes more dense as it moves from solid to gas

C. Matter becomes less dense as it moves from gas to solid state

D. Matter becomes more dense as it moves from gas to solid state

D) Matter becomes more dense as it moves from gas to solid state

A gas expands to fill up the container of whatever shape or size. As it cools to a solid, the molecules get closer together and don't move as much (the molecules still will vibrate and move somewhat even in solid form). So effectively the volume of the object shrinks while the amount of mass stays the same. This is why the density increases when going from gas to solid.

radioactive decay occurs in unstable atomic nuclei – that is, ones that don't have enough binding energy to hold

the nucleus together due to an excess of either protons or neutrons.