Why is mercury used in thermometer instead of water?

Answer 1

Mercury is a good conductor of heat and it expands to certain levels when heated to certain temperatures.

In addition:Water would freeze when the temperature went below 32 degrees F. or 0 degrees C. See the related link for more information.

Mercury has a higher boiling point and hence would not evaporate after 100 degree Celsius, like water, and this enables us to measure temperatures beyond it but if we see that as mercury is an good conductor of heat and it is expand to its level when we heat

Answer 2

1). A water thermometer wouldn't be too useful for temperatures below 32° F (zero° C).

Mercury remains liquid down to -78° F (-61° C).

2). Water's maximum density occurs at 39° F (4° C). That would have to be the mark

at the bottom of the thermometer. Water would rise in the tube at temperatures

above or below that.