Definitions for a text’s vocabulary words can be found in the glossary.

 That is true. You can find definitions for the tex's words in a glossary. 

Gasses as an state of matter are far apart and spread out.

Doulingo is good. you can also watch movies that are in french, i am using this tactic  for japanese  and it a lot. listing to music with  french  lyrics would work well too because  you could absorb  the words while having fun.hope this ! : )