1. Can Crushing
http://www.youtube.com/watch?v=QVayky_b-6U
In this demo, we poured a little boiling water to can, then we put a flame under the can to heat it, then we put it upside down into the a bowl of water, and a there was slight "bang" and the can crumpled. One might wonder why this would occur, it seems to defy the laws of chemistry. However, if one thinks this, then one does not really know the laws of chemistry at all in the first place, but only a select few do. As for the explanation, the can crumpled because the air pressure in the can is equal to the air pressure outside it. Thus there are no overall forces. However, when the water is boiled, lots of steam is produced, which then pushes air out the can, until the can is completely filled with steam. The steam has the same pressure as the air outside the can, so nothing occurs yet. But once the can is placed upside down in the bowl of water, the steam cools and turns back into a liquid, and it thusly does not have the same pressure as the air outside the can. The inside of the can becomes a vacuum, and with no pressure inside the can to fight the much higher air pressure outside the can, the air crushes the Coke can. I also lied, i will be showing video and photos, just not from class.
2. Stuck to the ground
http://www.youtube.com/watch?v=zqyuaMqOEGA
The second demo, Mr. Lieberman put a vacuum device clamped onto a table and then onto the floor. He then challenged anyone to try to lift up the device. Because of the intense air pressure, no one without the use of performance enhancing drugs would be able to lift it up because the vacuum sucks up all the air. When you lift up the clamps however, it is possible for you to lift it up, because the intense air pressure is let out.
3. The Vacuum
http://www.youtube.com/watch?v=Ct4AqODwhI8 In the third demo and final demo, Mr. Lieberman put someone in a plastic garbage bag with a very tight air seal. With such a tight air seal, there was no air in the bag. with no air in the bag, Alex the demonstrator began to feel more compressed and with nothing to resist, the air pressure outside the bag compressed on to him. It was very interesting and one thinks we learned a lot because chemistry is better explained through demos than through lectures.
Throughout the class we took some interesting notes on pressure. We discussed some formulas and concepts on pressure in gases.
Formula for pressure:
We also learned some standard pressure units and values that include:
A. 1 standard atmosphere
B.101.3 kPa
C.760 mm Hg
D.760 torr
E.14.7 lbs/in2
Apparently you use these to convert from unit to unit. One may wonder why there is not just one unit for all science, but that is merely wishful thinking. Due to that, here is how you convert from pressure units.
I. Converting between atmospheres and millimeters of mercury.
One atm. equals 760.0 mm Hg, so there will be a multiplication or division based on the direction of the change.
Example #1: Convert 0.875 atm to mmHg.
Solution: multiply the atm value by 760.0 mmHg / atm.
Notice that the atm values - one in the numerator and one in the denominator - cancel, leaving mmHg. So like in stoich, u want to the units to cancel, and once the units cancel, the rest is fairly easy multiplication done on a calculator. It is important not to have a nervous breakdown about the complex-sounding units, for they merely sound and are written like that to inspire awe and wonder. There you go, and I hope you learned a lot about pressure in gases.
Homework: Do pressure worksheet and begin completing webassigns unless they are not up yet, in which case, do not complete the webassigns, because it is technologically feasible. I suppose you could make your own webassign and then complete that, but one doubts the likelihood of that. Thank you.
Next Scribe: Bram Hill who sits in the front row to the left.
No comments:
Post a Comment