Generate an overlapping word between the given two sentences. When you find the overlapping words, they don't have to match exactly, e.g., "survival" and "survive" are valid overlapping words. Little words like "the" or "of" don't count! You must generate significant words which are not the stop words.

Sentence1: when a gas in an open container evaporates , that gas spreads out into the air. 
Sentence2: If you place gas in an open box it will evaporate and spread out into the air.
gas

Sentence1: Complex chemistry is needed to carry out all the functions of life. 
Sentence2: Chemistry is primarily concerned with matter, energy, and their interactions.
chemistry

Sentence1: Recycling is the reuse of material. 
Sentence2: Reusing material reduces the resources needed to make something.

material