Ideal Gas Laws (Third Day)

Spring 2015
3rd of March's Class

Pressure and Volume and Temperature

Class began with Professor Mason pouring water into an aluminium can and heating it up to an extreme heat with a blowtorch. After that, he immediately placed it upside down into a container of cold water. Image is shown below.

The aluminium can imploded immediately upon contact with the cold water. The aftereffect is circled in the image on the right. The steam that was produced pushes the air out of the aluminium can and occupied its full volume. Hence, it can be said that water vapor had replaced air's volume within the can.

However, when the can was placed into the cold water container, the sudden drop in temperature causes steam's volume to be reduced dramatically as it is converted back into its liquid form. The drop in volume means that the pressure within the can was reduced too.

Since there is now a difference between the pressure inside and outside the can, and also that the pressure outside the can is now greater than the pressure inside, the pressure from the outside would cause the can to crumple inward.

He then repeated a similar experiment but this time, he heated the can up without water inside. Essentially heating up the air within the can to high temperatures. After that, he immediately put it into cold water.

The first image above shows the empty can being heated up. The second image right below it, shows that it seemed like nothing happened to the can. However, cold water from the container had actually entered into the aluminium can.

In the shaky video above, in the first few seconds, we can see that the pressure rises as the temperature rises. After which when the temperature drops, we can see that the pressure decreases as well.


Ideal Gas Laws

Ideal Gas Laws are dependent on three variables: Pressure, Volume and Temperature. The Professor led us in an experiment where we would empirically determine their relationships, through the observation of graphs.

In the experiment, there were 3 water baths at different temperatures: Cold, Hot and Room Temperature.

There was supposed to be a video on the experiment, but its file size was too large and so I would be unable to upload it.

Above is the graph produced during the experiment, it shows that Temperature and Volume is directly related, with the pressure being kept constant. The values for each variable can be seen on the left side of the image above.

Using the 2 different forms of Ideal Gas formula, we can use their respective constant to arrive at Avogadro's number.

The two images above shows a balloon that underwent a reduction of pressure. The one on the left happened before the pressure was released from the bell. What happened after pressure was reduced in the bell, was that the balloon bloated up in size like the image on the right. This is a visual experiment to prove that lower pressure causes volume to increase.

The video above shows what happened when pressure is re-introduced into the bell. The increase in pressure causes the volume of the balloon to shrink. Professor repeated the experiment with marshmallows.

The same effects can be seen happening on the marshmallows as it was on the balloon. However the marshmallows ended up saggy and wrinkled by the end. According to the few students, that ate a piece of the marshmallow after the experiment, the texture of the marshmallow also changed to be more chewy.

In summary, we learnt of the relationships written above for this day.