Gas
This video presents the same text shown beside it, spoken and on screen. It adds nothing the text does not say.
State
A gas is a state of matter that expands to take both the shape and volume of its container.
Show
A small amount of helium released into an empty room spreads to fill the entire space, not only the lower portion.
Watch for
Students often assume a released gas sinks and pools at the bottom like a liquid, instead of spreading to fill the space.