Atmospheric pressure 1Atm or 100 kPa?

  • Thread starter flatmaster
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  • #1
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?
 

Answers and Replies

  • #2
mgb_phys
Science Advisor
Homework Helper
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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
 
  • #3
flatmaster
501
2
ok. average atmospheric pressure = 1 Atm and that's that. Good enough for now. I'll let them be confused later.
 
  • #5
flatmaster
501
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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.
 
  • #6
Borek
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Could be a good point, but... where do you get 4.5 atm from?
 
  • #7
flatmaster
501
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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.
 
  • #8
Borek
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3,659
So I guess lake is 45 m deep?
 

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