Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

Q: Deep currents are caused by differences in density at the top and bottom of the ocean.

A: What is caused by differences in density at the top and bottom of the ocean?
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Q: Changing the shape of an elastic material gives it potential energy.

A: Changing the shape of an elastic material gives it what type of energy?
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Q: A solution forms when one substance dissolves into another.

A:
What forms when one substance dissolves into another?
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