Chemical Technology Chapter 11 Investigation 1: Exploring Gas Pressure (and Converting between Units) Begin by taking so

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Chemical Technology
Chapter 11
Investigation 1: Exploring Gas
Pressure
(and Converting between Units)
Begin by taking some time to read through the PowerPoint
slides on Gases
Pressure is defined as the force/area. The measure
of Air Pressure is the force that molecules of air causes when they
collide with the sides of the container.
Let’s investigate the concept of air pressure at the
molecular-level.
Open up this simulation by PHET on gas
properties.
Click on Energy twice to open that part of the
simulation.
Click on the + in front of particles and injection
temperature to open those menus.
Note on the left, you can monitor the average speed of
the particles and see the graphing of the speed of the
particles.
In the particles you have the choice of heavy (blue) or
light (red) gas particles, for example Ne vs He.
Record the following
Width of the box with units (click the box in front of
width) _______________
Injection Temperature (units!)
_______________
Click on the “Fast Forward” double arrow to introduce 50
heavy particles to the box and watch the pressure
gauge.
When did the pressure gauge start to measure a pressure?
(Specifically, what had to HAPPEN before the pressure gauge
began to record a pressure?)
(You can hit the double arrow rewind to remove the 50 particles if
you need to watch it again.)
Watch the Average Speed and the Pressure, once these
values seem to fluctuate around the same value
Record the Pressure and Ave. Speed in the table
below
Add another 50 particles (100 total
particles)
Record the Pressure and Ave. Speed in the table below
PUMP IT UP. Hit the fast forward until you have
500 particles and
Record the Pressure and Ave. Speed in the table below
Table 1:
Data for the Blue particles with a box width of 10.0nm and
an injection temperature of 300K
# blue particles
Pressure (atm)
Ave Speed (m/s)
50
100
500
Which of those two values changed the most?
.
Clear out the box by hitting the orange button in the
lower right corner.
Repeat the simulation this time using the lighter (red)
gas.
Table 2:
Data for the Red particles with a box width of 10.0nm and
an injection temperature of 300K
# red particles
Pressure (atm)
Ave Speed (m/s)
50
100
500
Which of those two values changed the most?



.
Notice that the pressure for the heavier blue and the
lighter red are very similar for the same size
sample.
Is that true for a mixture of gases? Let’s test
that. Inject 50 red and 50 blue (100 total). What is
the pressure and is it about the same as a sample of 100 pure red
or 100 pure blue particles? Explain. Provide data to
support your answer.
The Average Speeds are different.
The Kinetic Molecular Theory of Gases relates the
properties of gas by understanding that the gas particles in any
sample are constantly moving and the energy of motion is kinetic
energy, KE = ½ (mass)(speed)2 .
The particles in the sample will have around the same
AVERAGE Kinetic Energy for a given temperature. So the
heavier blue gas particles had a (faster or slower) average
speed than the lighter red. Also note that not all particles
are moving at exactly the same speed and that is why we can look at
the average.
Air Pressure is directly related to the number of
particles colliding with the sides of the container. As we
can see also from the simulation that the gas particles spread out
throughout the entire box. So a sample of gas will spread out
to fill the container. If you put your mouse on the handle next to
the thermometer, you can slide it to the
left.
The gas particles now have a “new box” like letting the
air out of a balloon.
From the PowerPoint slides, what are the unique
properties of a gas?
The common units for measuring pressure are
atm (atmospheres)
psi (pounds per sq. inch)
mmHg or inHg (the height of the column of Hg in a
glass tube in a manometer).
bar
You can find the equivalences in this PDF
document.
Using the document above, Complete the following
conversions.
The air pressure in Denver, Colorado (which is at an
elevation of 5280 ft above sea level), averages about 24.9 inches
of mercury. Convert this pressure to:
(Please remember to show all of your work!)
atm
mmHg
Convert each pressure measurement to units of atm
(please show your work):
2.38 x 105 Pa
127 psi
455 torr