Steve Royer age 11. o Sperm Oaks Call ‑for his question:

Why doesn’t mercury freeze in cold weather?

A mercury thermometer can register the. temperature far  far below the freezing point of water. For mercury stays in liquid form between 675 degrees and minus 37.9 degrees Fahrenheit. But should the weather become 40 degrees below zeros or lower the mercury will freeze up solid. In such cold temperatures it is unable to expand and contract in the glass tube. In some blizzards in the Yukon a mercury thermometer would be useless.

For such cold places we use a thermometer in which alcohol does the work of the mercury.. Maybe you have seen thermometers in which the alcohol in the tube is colored red or blue. Such a thermometer can register temperatures as low as 100 degrees below zero. At this point the alcohol freezes solid.

Why don’t we use alcohol in all our thermometers? Because alcohol has a low boiling point. At 150 degrees. it begins to bubble and boil. It is then unable to give an accurate measure of the temperature. Mercury stays reliable for measuring temperatures up to 675 degrees  at which point it begins to simmer and boil.