Atmospheric pressure 1Atm or 100 kPa?

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Discussion Overview

The discussion revolves around the definition of atmospheric pressure, specifically whether it should be considered as 1 Atm (101,325 Pa) or 100 kPa, following a redefinition in 1999. Participants explore the implications of these conventions for educational purposes and practical applications.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Homework-related

Main Points Raised

  • Some participants note that atmospheric pressure is commonly defined as 1 Atm = 101,325 Pa, while others reference a Wikipedia entry stating it was redefined to 100 kPa.
  • One participant mentions that the choice of convention may depend on the organization, citing IUPAC's use of 100 kPa and NIST's use of 101.3 kPa.
  • Another participant expresses a preference for sticking to SI units, suggesting that if one uses Atm, they should use 1 Atm, but if using SI, they should use 100 kPa.
  • One participant argues that using Atm allows for easier comparisons in specific contexts, such as pressure at different depths in a lake or at the Earth's core.
  • There is a question raised about the source of the 4.5 Atm figure mentioned in relation to lake depth, with a later reply suggesting it corresponds to a depth of 45 m.

Areas of Agreement / Disagreement

Participants express differing views on which convention to use for atmospheric pressure, with no consensus reached on a preferred standard. The discussion includes both support for traditional definitions and the newer SI-based approach.

Contextual Notes

Participants acknowledge variations in definitions and standards across different organizations, which may lead to confusion in educational contexts. The discussion also highlights the importance of unit choice in scientific communication.

Who May Find This Useful

This discussion may be of interest to educators developing curriculum materials, students learning about atmospheric pressure, and professionals working in fields that require precise definitions of pressure standards.

flatmaster
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Ignoring normal variations, I've always been told that atmospheric pressure is...

1 Atm = 101,325 Pa

However, Wikipedia says atmospheric pressure was re-defined in 1999 to be exactly 100 kPa. This would mean that atmospheric pressure is now 0.98692 Atm.

http://en.wikipedia.org/wiki/Atmospheric_pressure

I'm writing a lab activity for high school students. From what I've read, it seems that both conventions are used. Which convention should be used?
 
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it depends who you work for !
IUPAC use 100Kpa but NIST use 101.3Kpa, as do most ISO standards.

None of these change the fact that the average air pressure is 101.3kpa
 
ok. average atmospheric pressure = 1 Atm and that's that. Good enough for now. I'll let them be confused later.
 
Using Atm allows me to compare 1Atm to 4.5 Atm at the bottom of a local lake and 3,000,000 Atm at the core.
 
Could be a good point, but... where do you get 4.5 atm from?
 
Borek said:
Could be a good point, but... where do you get 4.5 atm from?

It's a local lake. I calculated it myself from the depth.
 
So I guess lake is 45 m deep?
 

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