A balloon full of helium slowly deflates. What best explains why the balloon shrinking is an example of a physical change? The helium has changed state from gas to liquid.
Helium never undergoes chemical reactions.
A physical property of the helium gas, the volume, has changed.
Helium has physically escaped from small holes in the balloon.

Crinoids, also known as sea lilies, appear to be sea plants but are not plants at all. crinoids are an echinoderm species which uses anchoring structures called holdfasts to attach themselves to the sea floor. crinoids were most abundant in pennsylvania during the mississippian period, which ranged from 375 to 320 million years ago. fossils of the crinoids shows that during most of this time pennsylvania was that provided favorable conditions for crinoid growth. a) glacial terrain b) a dry and sandy plain c) mostly mountain ranges d) covered by warm, shallow seas