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.

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.

A: Propane
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Q: Sentence1: An electric current is a flow of electric charge. 
Sentence2: a magnet moving in a coil of copper wire can cause a flow of electric charge.

A: charge
****
Q: Sentence1: weathering means breaking down rocks from larger whole into smaller pieces by weather. 
Sentence2: weathering can be gravel breaking down from larger into smaller pieces.

A:
breaking
****