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

Q: Water leaves ponds and lakes through evaporation and also as outflow.

A: Water leaves ponds and lakes through evaporation and also as what?
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Q: To determine the atomic weight of an element, you should add up protons and neutrons.

A: How do you determine the atomic weight of an element?
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Q: Calculations are described showing conversions between molar mass and density for gases.

A:
Calculations are described showing conversions between molar mass and what for gases?
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