sentences: helium is less dense than air & a balloon is a kind of container & a popped is filled with cube oil ->  a balloon filled with helium is an example of a container contains a substance less dense than air  a balloon filled with helium is an example of a container contains a substance less dense than air & if a exercising contains a desk with more filings than land then that preference june stay upward -> the balloon filled with helium may move upward if released