Turn the given fact into a question by a simple rearrangement of words. This typically involves replacing some part of the given fact with a WH word. For example, replacing the subject of the provided fact with the word "what" can form a valid question. Don't be creative! You just need to rearrange the words to turn the fact into a question - easy! Don't just randomly remove a word from the given fact to form a question. Remember that your question must evaluate scientific understanding. Pick a word or a phrase in the given fact to be the correct answer, then make the rest of the question. You can also form a question without any WH words. For example, "A radio converts electricity into?"
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Question: Fact: substances reacting with one another causes them to vibrate.

Answer: what does substances reacting with one another cause?


Question: Fact: the population divided by the area is the average number of individuals per unit of area or volume.

Answer: What is the average number of individuals per unit of area or volume?


Question: Fact: the Moh's scale of hardness is used by scratching the materials.

Answer:
the Moh's scale of hardness is used by doing what to the materials?