Mary Ann,
   Many barometers today use the equivalent of a balloon stretched over a pressure sensor to measure pressure. No mercury needed!! Depending on your budget, you might want to check out the hand held Kestrels at this website.  These are nice handheld instruments that show temp, pressure and wind speed. The more expensive units do even more. They are easy to operate and you could have your students conduct their own weather investigations.
   Otherwise, when I taught HS, I had the same difficulties you are having. I often use the analogy of a swimmer's ears hurting when they dive to the bottom of a pool and relate that to use living at the bottom of an "ocean of air".

-Kyle Gray

Mary Ann Mutrux wrote:
[log in to unmask]" type="cite">Dear Folks,
  I am a new member.  I am looking for a place to get ideas and trouble shoot for teaching Earth Science for Teachers at Missouri State University in West Plains Missouri.  I have been teaching grades 7-12 over the last 25.5 years in the rural Ozarks (a great place to do geology - Karst heaven with great igneous knobs).  I am teaching this college class as an adjunct instructor.  This is the 3 year that I have taught the class in the last five.  I have been struggling with student misconception for years!   I have a MS in education.  I have read many books on the brain and learning (Pat Wolf, Mel Levine, and many more).  I did find Heather Percovic and Robert Ruhf study published in the Journal of Geoscience Education (May 2008) very interesting and useful.  My inquires with Heather have brought me to this list serve (this is my first).  I have signed up to access and use the Geoscience Concept Inventory.  I am looking forward to making up a test after my account is completed.  

I have a ton of questions.  Lets start with one.

Barometers!   First of all, no one uses one anymore!  The data is just given on web forecasts.    The school can afford to buy one.  I have used the balloon stretched over the can in the past to measure air pressure.  This method is not exciting, it is difficult to "see" any significant difference over a period of time.  Any ideas?  The safety school personnel took my mercury away years ago (yes - I had some for a HS lab, I would only "show" students - this tells you how long I have been around).  How to I get the concept of air pressure / forecasting across to pre service teachers and 8th graders without messing them up and without a real barometer.  I do have on old one that was broken I have taken apart that I show.  

Mary Ann Mutrux
Middle School Science Teacher