TASK DEFINITION: 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.
PROBLEM: Sentence1: an automobile engine transforms chemical energy into mechanical energy. 
Sentence2: cars transform chemical energy into mechanical energy.

SOLUTION: chemical

PROBLEM: Sentence1: if an object in a fluid is more dense than that fluid then that object will sink in that fluid because of gravity. 
Sentence2: Most seeds are more dense than water.

SOLUTION: dense

PROBLEM: Sentence1: Heterotrophs are living things that cannot make their own food. 
Sentence2: Green plants are not Heterotrophs.

SOLUTION:
Heterotrophs