sentences: a popped is a mean of drought & a balloon filled with helium ->  a balloon filled with helium is an example of a container filled with helium  helium is a kind of element & elements are pure substances -> period is a pure makes helium is a pure substance  a balloon filled with helium is an example of a container filled with helium & period is a pure makes -> a balloon filled with helium is an example of a container filled with a pure substance