can water be used ina barometer instead of mercury?why?

Answer 1

Yes it can, but since water has a much smaller density than mercury, your barometer would need to be significantly longer than one with mercury.

Answer 2

It depends on the use of the barometer. If you use it to measure absolute atmospheric pressure (ambient pressure) then a water column barometer has its limits. As said above one of it is the size, but the other limit is the vacuum that is above the water. It will make the water boil at room temperature and you will have gaseous water instead of a vacuum above the water. The pressure there would no longer be zero and the reading of the water barometer would be wrong.

But if you need a differential barometer to measure small pressure changes relative to ambient pressure a water barometer is the ideal instrument for that. 1mm of differential level in water would be about 1/10'000 of our ambient pressure at sea level.

Answer 3

YES - but a mecurial barometer has to be around 32" high, because at sea level a vacuum will support 29.92" of mercury and the pressure will vary a few inches.
On the other hand a vacuum will support 34 FEET of water. You would need a tube around 35 feet long to account for variances - that's why the use mercury, just easier to handle.

Look up conversions for 1 atmosphere

1 atmosphere = 33.9 feet of water at 4C = 29.92 " hg @ 0C

Answer 4

YOu just need a thicker tube. Also water evoportes which mercury doesn't do.

Answer 5

You could use water, but the changes in volume, especially at the temperatures we are normally measuring (0 to 100 degrees F) would be so small as to be nearly immeasurable. Mercury is ideal because its volume changes dramatically at the temperature range we are interested in.

Answer 6

Yes, but it will be 32 feet high.