Factors Affecting Gases

            Hi everyone. On Friday we had a very interesting lesson on the different factors that affect gases and how they affect them. These factors were pressure, temperature, and volume. There were several demos and explanations for these that I will  go over. I have pictures of the actual demos we did in class and not ones off the internet.

Boyle's Law
        The first three demonstrations were proving this law. The law states that as pressure decreases, volume increases or P1V1=P2V2 where P is pressure and V is volume.
               
Demo #1 Balloon in Vacuum Pump

 As you can see, there is a tube hooked up to the container that sucks out all of the pressure around the balloon. When this happens, the volume of the balloon increases...

 The same procedure is done with shaving cream and the result is the same.

Again, the pressure decreases and the volume increases...

 This was also done with a marshmallow, but unfortunately i could not get a picture. The same exact thing happened with that.

Charles's Law
         This law states that as temperature decreases, volume decreases, or volume is directly proportional to temperature. The formula for this is V1/T1=V2/T2 where V is volume and T is temperature.

The example of this was a demonstration that used liquid nitrogen, which is extremely cold, to lower the temperature of the air inside of the balloon resulting in a decrease in volume.

                                                                     

  Here the balloon is being stuffed into the liquid nitrogen. It takes a while for the balloon to deflate and shrivel up. It was difficult to get a picture of the shriveled up balloon because once it was taken out of the liquid nitrogen its volume started to increase rapidly because of the rise in temperature.

Gay Lussac's Law 
          This Law states that the pressure and temperature of a gas are directly related. The equation for this is P1/T1=P2/T2. 

To demonstrate this, and instrument that measures pressure was put into the liquid nitrogen to see if the pressure would lower along with the temperature.

         
         
         









Before the it was put in, the device read 15 atm and after it read 4.25 atm, so the pressure did decrease by a lot.

The Combined Gas Law puts all three equations into one, which makes it much easier to remember.
        The equation is P1V1/n1T1=P2V2/n2T2. P is pressure, V is volume, n is moles, and T is temperature. This equation is used in problems where there are two sets of variables, such as numbers 9, 11, and 12 in the homework.

Finally, there is the Ideal Gas Equation, in which the constants of the previous laws have been combined to form the gas constant R. This equation is PV=nRT where P is pressure, V is volume, n is moles, R is a constant for pressure (either 0.0821 atm L/ mol K or 8.314 kPa L/ mol K), and T is temperature. This is used in a problem where there is only one set of variables, which includes nearly all of the homework problems.

To end class on a good note, we had fun with liquid nitrogen and did activities such as watching Mr. Lieberman chuck frozen orange at the wall, pouring liquid nitrogen on the floor, and pouring it on Charles.

Homework: Ideal Gas Law worksheet and work on WA

The next scribe is.....Kevin L. who sits next to me