Question

Explain why mercury is used as a barometric fluid, instead of water.
[3 Marks]

Answer 1

Mercury is used as a barometric fluid, instead of water because:

(i) Mercury being 13.6 times denser than water requires less tube length to represent a given amount of pressure.
(1 mark)

(ii)In a simple barometer, 1 atmosphere of pressure is represented by 760 mm of mercury in the coloumn. For the same pressure, the length of water coloumn required would be 10336 mm, which is roughly over 10 m.
(1 mark)

(iii)Water is also highly succeptible to changes in temperature. Thus, mercury is better suited over water as a barometric fluid.
(1 mark)