The freezing point of pure water is 32 degrees Fahrenheit (0 degrees Celsius). However, by simply adding a common household ingredient, you then can easily cool the water 20 degrees past the freezing point, and still keep it in liquid form.
How is this possible?
By adding salt to water, you lower the freezing point of the water. If you add enough, it is possible to get it 20 degrees below the typical freezing point.
Today's brain teaser courtesy of Braingle.com.