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Posted by Ryan On November - 4 - 2008 0 Comment

Units of Gas Pressure:

Pressure is commonly measured in three different units.

Torr – the original unit of pressure is named so in the honor Evangelista *
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Units of Gas Pressure:

Pressure is commonly measured in three different units.

Torr – the original unit of pressure is named so in the honor Evangelista Torricelli. He found that if you placed mercury in a gas evacuated tube at sea level, the atmospheric pressure would force it to rise 760 mm. Thus, the pressure exerted by the gas is strong enough to displace 760 mm of Hg or 760 torr.

So for convenience, we equate the atmospheric pressure (760 torr) to be our standard and equate that to 1 atmosphere or 1 atm. Thus, it is common and much simpler mathematically to use 1 atm as our standard pressure.

The final unit, which is more common around the world, is kilopascals (kPa). One atmosphere is equivalent to 101.325 kPa. This is equivalent to how many Newton’s per square meter or force per unit area exists, which is essentially the definition of pressure.

1 atm = 760 torr = 101.325 kPa

Demo: Dry Ice Bomb

In this video different proportions of dry ice (frozen Carbon Dioxide) is mixed with water and placed in a sealed 2-Liter soda bottle. Mixing the dry ice (-78.5 C) with luke warm water (above 0 C) will sublime (change from solid to gas) the carbon dioxide, producing an increasing amount of gas. This increase in the number of gas molecules will increase the pressure until the container can no longer hold it – boom!

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+ CategoriesTorricelli. He found that if you placed mercury in a gas evacuated tube at sea level, the atmospheric pressure would force it to rise 760 mm. Thus, the pressure exerted by the gas is strong enough to displace 760 mm of Hg or 760 torr.

So for convenience, we equate the atmospheric pressure (760 torr) to be our standard and equate that to 1 atmosphere or 1 atm. Thus, it is common and much simpler mathematically to use 1 atm as our standard pressure.

The final unit, which is more common around the world, is kilopascals (kPa). One atmosphere is equivalent to 101.325 kPa. This is equivalent to how many Newton’s per square meter or force per unit area exists, which is essentially the definition of pressure.

1 atm = 760 torr = 101.325 kPa

Demo: Dry Ice Bomb

In this video different proportions of dry ice (frozen Carbon Dioxide) is mixed with water and placed in a sealed 2-Liter soda bottle. Mixing the dry ice (-78.5 C) with luke warm water (above 0 C) will sublime (change from solid to gas) the carbon dioxide, producing an increasing amount of gas. This increase in the number of gas molecules will increase the pressure until the container can no longer hold it – boom!

Categories: Gases, States of Matter, Videos

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