Soft Water or Hard Water?Science brain teasers require understanding of the physical or biological world and the laws that govern it.
Two friends, Fred and Liz, were having a fun night out. They went to the bowling alley, bowled for a while, went to the bar, then left. They went to Liz's apartment, at which Fred had never been before. Out of the blue Fred said, "How much do you want to bet I can figure out, without guessing, if the water in your apartment is hard water or soft water?" Liz thought to herself and decided he wouldn't be able to tell, so she bet him twenty dollars. They bought some cheap soap at the local gas station, and a minute after they got back to her apartment, he told her the water was soft. He was right, and Liz handed him a twenty dollar bill. How did he know it was soft water so fast?
HintHe figured it out at the sink.
AnswerAll he had to do was wash his hands. When you take a bar of soap and wash with soft water it leaves your skin soft, and your hand will glide right over it. On the other hand, (pun intended) when you take a bar of soap and wash with hard water, the soap reacts to the minerals in it and forms a very, very small layer of soap over your hands, which leaves it rough. All Fred had to do was wash his hands and he instantly knew if it was soft or hard water depending on how his hands felt afterwards.
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