5. gases

ideal gases

In Journey 5, we learned about ideal gases. Ideal gases are non-polar and have high temperatures, low external pressures, and low molecular masses. Ideal gases can be explained by the Ideal Gas Law. This equation helps model and predict the behavior of gases. The Ideal Gas Law is PV = nRT - where P is the pressure of the gas (in atmospheres), V is the volume (in liters) taken up by the gas, T is the temperature (in Kelvin) of the gas, R is the gas constant (0.0821 liter atmospheres per moles Kelvin), and n is the number of moles of the gas.

Vacuum Candle Experiment: To help us understand Ideal gases, we performed a vacuum candle experiment. The goal of this lab was to determine why the water rises after a candle flame burns out. The materials we used were a dish, water with added food coloring, candle, glass, and a lighter. In the experiment, we placed a candle on a dish filled with water, lit the candle with the lighter, and covered the candle with an inverted glass. We then observed. We found that after a little while the candle flame went out, and the water level inside the glass began to rise.

(1) The candle flame heated the air in the glass

(2) The hot air expanded

(3) A vacuum was created

We concluded that the following occurred. (1) The candle flame heated the air in the glass. (1) The hot air expanded. When the flame went out, the air in the glass cooled down. That cooler air then contracted. As this air contracted, (3) it created a vacuum, creating a lower pressure inside the glass compared to the higher pressure outside of the glass. It is this higher atmospheric pressure on the outside of the glass that pushed the water in the dish to the inside of and up into the glass.

Flying Teabag: To further study Ideal gases and the Ideal Gas Law, we performed an experiment using a tea bag. The goal of this lab was to create a flying tea bag. The materials we used were a tea bag, scissors, and lighter. In this experiment, we cut the top of a tea bag, emptied the tea, and unfolded it and propped it up into a cylinder. We then lit the top of the cylinder tea bag and observed. The cylinder tea bag burned from the top and headed downward. When it was smaller and while the bag was still on fire, the small remaining bag rose up quickly off of the table.

We concluded that as the flame burned down the cylinder, it heated the inside air of the tea bag cylinder. When the inside air temperature increased, the volume increased. From the Ideal gas law, as the volume increases, the pressure decreases and as result the air will become less dense. The hot air molecules will rise and take the remaining tea bag up.

Balloon Pressure Chamber: As we continued our exploration of Ideal gases, Ramsey performed an experiment dealing with gas pressure and a balloon. For the experiment, he placed a slightly inflated balloon into a pressure chamber. (Note that at first the pressure inside of the balloon was equal to the pressure outside of the balloon.) He then removed the air from the chamber, and we observed. We found that the balloon expanded.

From our observation and discussion, we concluded that a vacuum was created in the chamber. From the Ideal Gas Law, we understand that the volume of the balloon increased because the pressure decreased. When the pressure was lowered, the air inside the balloon expanded to fill the vacuum created by the pressure chamber.

Collapsing Can Experiment: To further study ideal gases, Ramsey demonstrated another experiment for us. He heated a can and then submerged the can into a cold water bath. We observed. When the heated can was placed into with the cold water, it imploded.

We concluded that the pressure inside the can changed due to the drop in temperature. This is because when the soda can was plunged into cold water, the vapor condensed quickly and basically turned to water, which caused a vacuum to occur inside the can. There then becomes a large difference between the outside air pressure and the inside air pressure - causing the can to implode.

reflection

Overall, I found this part of honors chemistry class very interesting. I learned so much information about gases, and I found that I can apply the knowledge to daily life. As I have said in every part of Chemistry, Ramsey is an amazing teacher. I continue to learn very easily from him and enjoy all that he teaches.

As the last part of this phase of our class concluded, I prepared for the test. I did this by reviewing class notes, my labs, and the homework. I felt that I was prepared for the test.

Overall, I again enjoyed this portion of the class and find that I really like honors chemistry.

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