The most authoritative answer in 2024
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Alex Smith——Studied at Stanford University, Lives in New York City.
Pure
water (like clean
rainwater) is
soft water. It only becomes hard when it comes into contact with rock layers made up of compounds such as calcium or magnesium, and dissolves in it. Let us take
rainwater as an
example. The
rainwater may be slightly acidic because of some carbon compounds in the air from pollution.
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