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: Propane can be either a liquid or a gas. 
Sentence2: heat can be added to propane to change it's properties through the boiling process.
Propane

Sentence1: Hair helps to insulate and protect the body. 
Sentence2: most mammals have insulation that also protects the body.
body

Sentence1: sandpaper is used to smooth wooden objects. 
Sentence2: sandpaper is used to smooth bats.

sandpaper