Why water cannot be used in simple barometer?

Answer 1

Following are the reasons why Mercury and not water is used in a barometer:

1. Mercury is relatively denser than water, consequently the length of the column of water would have to be about 34 feethigh to exert pressure equal to that of the atmosphere while the column of mercury need to be only 30 inches to exert pressure equal to that of the atmosphere.

2. Mercury has a very low vapor pressure when compared to that of water. So it is more sensitive than water to the changes in the atmospheric pressure and rises more quickly to record the changes in the atmospheric pressure.

3. Mercury's freezing point is much lower than that of water's so it can record the atmospheric pressure at temperatures below that of 0 degrees centigrade.

4. Mercury does not evaporate easily so very little mercury vapor enters the vacuum above the mercury in the tube.

5. Mercury being a metal shines brightly and so can be used to read the markings on the tube easily.

Answer 2

Water is not suitable for use in a barometer because it is too dense and heavy, which would require a very tall column to measure small changes in atmospheric pressure accurately. Additionally, water can easily evaporate and create inaccuracies in the measurements. Mercury is traditionally used in barometers because it is dense, does not easily evaporate, and provides a more practical measurement system.

Answer 3

It would evaporate