Pressure: Gases

Due today:  -The Behavior of gases worksheet  (answer key has been posted on moodle)
Due tomorrow:  -Pressure worksheet

Today, we continued our introduction to pressure and gases with some more demos.  Below are the summaries of the demos.


1. Flask and paper

In this demo, a note card was placed on top a flask
 filled with water, then the flask was turned over.
Interestingly, the water did not spill from the flask.
This demo proves that pressure is everywhere
 pushing in all directions.  

      2.   Can Crushing

In this demo we heated an aluminum can filled with a little water.

Then, we placed this can top down in to a large beaker of cold water. The can

immediately crushed when it contacted the water.  Inside the can is low pressure

because of the water vapor.  And the outside or the atmosphere is high pressure.  That is why when placed in the water the high pressure crushes the low pressure.

3.  The Vacuum

For the third demo, we put someone into a large garbage bag an tried to get an air tight seal.  Then we turned on the vacuum and removed all the air from the bag.  This removed all the pressure surrounding the person in the bag which made it feel like there was more pressure pushing down on them.  Our lucky demonstrators were Madi, Georgia, and Mr. Lieberman.

4.  Stuck to the ground




This was an interesting demo that involved a device with two levers that when flipped down, the device would stick to whatever smooth surface it was on.  Xavier came up to try to pull it off the ground with a promise of breakfast from Mr. Lieberman if he did.  Xavier removed it without a sweat!  Breakfast for him!










Later in class we went over some notes on pressure.  In theses notes we discussed the different measures of pressure along with some formulas and conversions:

Formula for pressure:

 In case you are not sure what pressure is, it is: 

--the force created by the collisions of

 molecules with the walls of a container.

The molecules in the container move in a random
direction as shown to the right.

We also talked about how a mercury barometer works
as shown below:
.

Here are the standard pressure values and units that can be used for conversions:

• 1 standard atmosphere
• 101.3 kPa (kilopascals)
• 14.7 lbs/in2
• 760 mm Hg (millimeters of mercury)
• 760 torr

These standard values can be used to convert from unit to unit  as shown below:

99.6 kPa x 1 atm/101.3 kPa = 0.983 atm

0.983 atm x 760 mm Hg/1 atm = 747 mm Hg

Next scribe: Jeremy E.