In this video, we will be investigating Boyle's Law using the Go Direct gas
pressure sensor. The primary objective of this experiment is to determine the
relationship between the pressure and volume of a confined gas.
The gas we use will be air, and it will be confined in a syringe connected to a Go
Direct gas pressure sensor. When the volume of the syringe is changed by moving
the piston, a change occurs in the pressure exerted by the confined gas.
The pressure will be recorded as a Function of Volume on the Graphical
Analysis software. From that data, you should be able to determine what kind of
mathematical relationship exists between the pressure and volume of the confined
gas. The Go Direct gas pressure sensor can be connected via USB or via Bluetooth to
your platform. Platform can be a Chromebook, Mac computer,
Windows computer, iOS, or Android device. To get started, make sure you have
downloaded the free Graphical Analysis 4 app from our website,
or the appropriate app store. Since I will be taking data via Bluetooth,
I will first turn on my pressure sensor. I then open my Graphical Analysis 4 app and
select Sensor Data Collection.
I connect to my gas pressure sensor, and select Done. For this experiment,
I want to be able to tell the software what volume my syringe reads.
This requires a mode we call "Events with Entry." To set up my data collection,
I tap on the Mode button, then from the drop-down menu, select Events-Based.
Make sure Events with Entry is selected, and change the event name to Volume with
units of milliliters, and select Done. Now that my software is set up,
I want to prepare my pressure sensor. I take the syringe that shifts with my
pressure sensor and set it to 10 Milliliters. I then connect the syringe
Luer lock to my gas pressure sensor Luer lock, and make sure they are finger-tight.
I'm now ready to collect data by pressing the Collect button. No data is recorded
until I hit the Keep button. My live pressure reading is in this corner and it
is currently stable. Once I press Keep, the data point is recorded and the
software is asking me to tell it what the volume that, that pressure corresponds
to. Now, the syringe is reading 10 milliliters. However, there is 0.8
milliliters of volume inside the pressure sensor that I also need to account for.
So for every value I type in, I will need to add 0.8 milliliters to it.
So this volume is 10.8 milliliters. Press Keep Point, and now that data point is
recorded. Now, I'm going to move the piston to 5 milliliters,
and press the Keep button.
I can now relax the piston and type in 5.8 milliliters for that data
point, and Keep Point. I'm going to repeat this process for several different
volumes. Next, I will do seven milliliters.
Press Keep, and that is 7.8.
Now, I'm going to do 12 milliliters, Keep, 12.8. And finally, 15 milliliters.
Now, I can stop data collection once all my data points have been collected.
In looking at the data, we should be able to determine whether the mathematical
relationship between pressure and volume is direct or inverse.
We can check our educated guess with the curve fits built into Graphical Analysis.
To do that, we click on the Graph Tools icon, and tap on Apply Curve Fit.
Linear is the default, but we want to select the Power Fit, and then click
anywhere on the graph to get the data parameters. The Power value,
B, is very close to negative one. This confirms that it is an inverse
relationship. To further investigate the type of relationship that exists between
pressure and volume, a graph of pressure versus the reciprocal of volume can also
be plotted. To do this using Graphical Analysis, it is necessary to create a new
column of data, Reciprocal of Volume, based on your original volume data.
First, I want to remove the fit, and then tap on the dots in the Volume column and
select Add Calculated Column. I want to rename my calculated column to be 1 Over
Volume with units of one over milliliter. To enter the correct formula for the
calculation, select Insert Expression and select A Over X. Make sure Parameter A is
one, and column X is Volume. Select Apply. Make sure that 1 Over Volume is
displayed on the horizontal axis. If the relationship between pressure and volume
is an inverse relationship, the plot of pressure versus the reciprocal of volume
should be direct. That is the curve should be linear and pass through your data
points. Let's perform a Linear Fit on this data to see if that's correct.
From the Graph Tools icon, select Apply Curve Fit, and it is indeed an inverse
relationship. For more information about the Vernier Go Direct gas pressure sensor
and our Go Direct line of sensors, visit our website or email info@vernier.com.