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Mercury has a very low vapor pressure. Vapor pressure is the pressure exerted by the gaseous form of a liquid on the liquid itself when both states are in equilibrium. A higher vapor pressure means (which is known as a volatile substance ← [this statement is unclear and seemingly unrelated. I cannot determine its relevance, but perhaps it can help you]) more pressure is exerted by the ambient atmosphere on the liquid and hence it cannot rise easily to denote the pressure increase. Hence liquids with low vapor pressure are usually preferred as they can rise easily or they can show more sensitivity. Water has a relatively high vapor pressure, and thus is not as sensitive to changes in pressure as mercury is.
This is why when we measure pressure with water, we divide the water level change by 13.6, which is the ratio of the density of HOH to the density of Hg. Our answer changes from the non-standard pressure measurement in milimetres of HOH to the commonly-used milimetres of Hg
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.
Wiki User
∙ 13y ago
Wiki User
∙ 14y agoBecause mercury is heavier than water, therefore it takes more atmospheric pressure to make the mercury move. However, there are aneroid barometers, which don't have any fluid in them at all.
Wiki User
∙ 14y agoThe main cylinder of a barometer is a vacuume. Mercury is used because of its density and high boiling point. water would simply vaporise.
Wiki User
∙ 13y agoMercury is more heat reactive so it was more precise and the liquid went up and down more.
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What measures a barometer with Mercury?
Maybe you mean what does a mercury barometer measure. In which case the answer is atmospheric pressure.
A decrease in the height of a column in a mercury barometer means that .'s surface?
When air pressure increases, the mercury in a barometer rises.
When air pressuer increases what does the mercury in the barometer do?
Air is "pushed" into the open end of a barometer when the pressure is higher, meaning the mercury closer to the closed end of the barometer - where the pressure is measured - will rise.
What is in the space above mercury in a barometer?
The space above the mercury is airtight, there is no air above the mercury
What is a mercury barometer?
A mercury barometer is a device that measures air pressure. The key component that distinguishes it from other barometers is the metal mercury.
Which liquid is used in an aneroid barometer a mercury b alcohol c none?
mercury
What is a barometer with Mercury called?
A mercury barometer.
Types of Barometers?
anaeriod barometer and a mercury barometer
What are the Precautions for aneroid and mercury barometer?
Mercury barometer precaution
An aneroid barometer is different from a mercury barometer in that it does not contain?
Mercury
Why is mercury preferred to alcohol as a thermometric fluid?
what are the qualities of mercury over alchoholic as thermometric liquid
What type of barometer was invented first the aneroid or the mercury?
The first barometer that was invented was the MERCURY barometer. a mercury barometer consists of a glass tube open at the bottom end and partially filled with mercury. (:
What does a barometer has in it?
barometer has mercury inside it .
Which statement accurately describes a difference between a mercury barometer and an aneroid barometer?
One statement to accurately describe a difference between a mercury barometer and an aneroid barometer is that a mercury barometer is a closed tube containing mercury. An aneroid barometer is a closed, flexible container of gas.
What are the uses of a Mercury barometer?
A Mercury barometer is used to measure atmospheric pressure.
An increase in air pressure will cause the mercury in a barometer to?
When you increase air pressure the mercury in a barometer will rise. Conversely when air pressure decreases the mercury in a barometer will drop.
What is in a thermometer and a barometer?
A thermometer measures temperature - most are now electric but they used to have alcohol or mercury in them. A barometer measures air pressure - they are now electric but used to have air in them (in a bellows with a spring).
