Gas Laws

We thought about what happens when an object is cooled. 

Then we filled the tube with water and marked the height of water. Then, we blew on one side and marked the new height of the other side. Then we measured the distance between the lines and the diameter of the tube.

Next we found out that the calculation of the cross-sectional area can be skipped because it cancels out.

Next we looked for the relationships of V vs T, P vs T and P vs V.

As volume increases, pressure decreases when the temperature is maintained constant. This is called Boyle's Law.

First, my group predicted that pressure and volume have an inverse relationship although we didn't know which kind. Then, we set up a syringe with 10 cc and hooked it up to the pressure sensor and computer to record the pressure as a function of volume. Then we tried to find a function that could fit this behavior. We found an equation of the form y = 1/x fits best. This means that pressure and volume have an inverse relationship. Our prediction was confirmed.

Next we tried to predict the behavior of pressure as temperature changes and maintaining temperature. Our prediction is in the following picture.

Prof. Mason run the experiment and showed us how pressure changes with temperature. It showed that pressure and temperature have a linear relationship. This is called Charles Law II.

The set up for the Volume vs Temperature. Prof. Mason brought a very special syringe that has almost no friction. Hence, it can be used to record volumes as temperature changes while maintaining the pressure.

Following is the data recorded from the set up above and shows a Temperature vs. Volume graph. It depicts that temperature and volume have a linear relationship.

When we combine all these relationships together, we get the ideal gas law. It states that pressure is inversely proportional to volume, pressure and volume are proportional to volume, and pressure times volume divided by temperature is a constant.

The triple point is a temperature and pressure that makes a substance have a solid, liquid and gas phase.
The critical point is a temperature and pressure at which a substance's physical properties vary continuously.

Next we did a diving bell problem and we figured out the pressure of air when it's submerged and the height at which the water rises to. The pressure was 2.36 * 10^6 Pa and the height was so that there was 11 cm left of air.

 Then we predicted and tested the behavior of a balloon under relatively different pressures. The first picture shows the balloon at normal pressure.

Then, we released the pressure, and the balloon expanded.

And then, we let the pressure normalize, but the balloon shrunk more than it's starting size.

The most realistic explanation for this is that the air inside the balloon escaped and that's why the balloon got smaller.

Then we tried to do the same with marshmallows.

The marshmallows started at a regular size.

Then, when the pressure decreased, the marshmallows grew in size.

But, when the pressure normalized, the marshmallows got a lot smaller than before.

Apparently, the expansion of size released the air trapped inside the marshmallows, and, when the pressure normalized, it ended up shrinking.

Next we did the high altitude balloon problem.

First a free-body diagram had to be drawn. Then, the equations could be derived.

 Working with the ideal gas law, we got an expression that could be solved for the molar mass.

We solved for the density of air at the two different heights and plugged them into the force equation.

In order to illustrate the relationships in the ideal gas law, a 3D image is needed.

Also, the ideal gas law is a lie because it only works in very restricted environments. A more exact form is the Van der Waals Equation. This is one is a second degree equation and yields more accurate measurements. There are also a third degree and a fourth degree one.