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.

[EX Q]: 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.
[EX A]: Propane

[EX Q]: Sentence1: a switch is used to start the flow of current in an electrical circuit. 
Sentence2: The flow of electrical current powers a light bulb.
[EX A]: current

[EX Q]: Sentence1: safety goggles are used for protecting the eyes during experiments. 
Sentence2: plastic protects the eyes during experiements.
[EX A]:
experiments